Phylum Brachiopoda
 
 
             
                               
                     
         

NOTICE: Some brachiopod specimens in the MCZ collections may have identifications that are out-of-date and/or specimens may have been mislabeled. The list below is the culmination of the current identifications until the collection can be updated.

Subphylum Lingulifomea-
Class Lingulata
Order Lingulida

Order Acrotretida

Order Siphonotretida

Subphylum Craniiformea-
Class Craniata
Order Craniida
Subphylum Rhynchonelliformea-
Class Strophomenata
Order Strophomenida
Class Rhynchonellata
Order Orthida
Suborder Orthidina

Order Rhynchonellida

Order Atrypida
Suborder Anazygidina

 
           
 
-Species Descriptions -
 
 
SUBPHYLUM LINGULIFORMEA
 
 
CLASS LINGULATA
 
 
ORDER LINGULIDA
 

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Discina sp. Lamarck, 1819 - Description from Holmer and Popov, 2000

Description: Shell is irregularly subcircular and biconvex to convexoconcave. The ventral valve is cemented to substrate and the pedicle opening may be sealed in adults. Both valves have a subcentral apex. Shell has an ornament of concentric growth lines and fine costellae. The ventral interior has a high subtriangular median septum (probably attachment site of oblique internal muscle) extending a short distance posterior of the apex, partially closing pedicle opening, and almost forming pedicle tube. The lophophore is spiralophous.

Ecology: Epifaunal, filter feeders that attach by a highly muscular pedicle to some hard substrate.

 

    Discina sp., MCZ 145762            
   
MCZ 145762: 7mm long
           

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Discinisca lamellosa (Broderip, 1833) - Description from Holmer and Popov, 2000

Description: Shell is dorsibiconvex to concavoconvex and subcircular. Surface has an ornamentation of fine growth lines that may become lamellose peripherally, with or without fine ribs. The ventral valve has a large depressed area around the pedicle and internally has a small triangular median septum extending posteriorly from the apex to the listrium.

Ecology: Epifaunal, filter feeders that attach by a highly muscular pedicle to some hard substrate. Often attach to various rocky surfaces and mollusc fragments and can occur singly or in a cluster of many individuals.

 

    Discinisca lamellose, MCZ 145760            
   
MCZ 145760: 6.5mm long
           

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Lingula attenuata

Description:

Ecology: Infaunal burrowers and filter feeders.

 

    Lingula attenuata, MCZ 145783            
   
MCZ 145783: 2mm long
           

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Lingula curta Conrad, 1842 – Description from Grabau and Shimer, 1907 and Wilson, 1946

Lingula curta Conrad, 1842, p. 266, pl. 15, fig. 12; Hall, 1847, p. 97, pl. 30, fig. 6; Billings, 1863, p. 161, fig. 138; Grabau and Shimer, 1907, p. 195; Wilson, 1946, p. 18, pl. 1, fig. 4.

Description: Shell is small, obtusely ovate, and depressed convex. Length and width nearly equal, front is broadly rounded, and the shell outline is subcircular except for a slight irregularity at the beak. Beak is projected beyond the end of the margin of the shell. Surface is covered by elevated concentric growth lines.

Ecology: Infaunal burrowers and filter feeders.


    Lingula curta, MCZ 145761            
   
MCZ 145761: 4mm wide
           

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Lingula daphne Billings

Description:

Ecology: Infaunal burrowers and filter feeders.

 

    Lingula daphne, MCZ 145758            
   
MCZ 145758: 9mm long
           

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Lingula elongata Hall, 1847 – Description from Wilson, 1946

Lingula elongata Hall, 1847, p. 97, pl. 30, fig. 5; Billings, 1863, p. 161, fig. 135; Wilson, 1946, p. 18, pl. 1, fig. 5.

Description: Near parallel sides, a lack of radial striae, and a great convexity characterize this species.

Ecology: Infaunal burrowers and filter feeders.


    Lingula elongata, MCZ 145757            
   
MCZ 145757: 11mm long
           

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Lingula obtusa Hall, 1847 – Description from Wilson, 1946

Lingula obtusa Hall, 1847, p. 98, pl. 30, fig. 7; Billings, 161, fig. 137, Wilson, 1946, p. 10, pl. 1, fig. 3.

Description: An obtuse angle of the beak and a non-terminal position characterize this species.

Ecology: Infaunal burrowers and filter feeders.

 

    Lingula obtusa, MCZ 145754            
   
MCZ 145754: 18.5mm long
           

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Lingula quadrata Sowerby

Description:

Ecology: Infaunal burrowers and filter feeders.

 

    Lingula quadrata, MCZ 145753              
   
MCZ 145753: 29.5mm long
             
    Lingula quadrata, MCZ 145759              
   
MCZ 145759: 6.5mm long
             

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Lingula rectilateralis major Ruedemann, 1925 – Description from Wilson, 1946

Lingula rectilateralis Emmons, 1842, p. 399, fig.6; Grabau and Shimer, 1907, p. 195, fig. 288c; Ruedemann, 1912, p. 91, pl. 4, fig. 1
Lingula quadrata Hall, 1847, p. 96, pl. 30, fig. 4, p. 285, pl. 29, fig. 1.
Lingula rectilateralis major Ruedemann, 1925, p. 110, pl. 11, fig. 1, 2.

Description: Shell is large with nearly parallel sides and has an elliptical form. The front of the shell is regularly rounded and the anterior margin is more or less truncated. Surface is marked by radiating striae.

Ecology: Infaunal burrowers and filter feeders.

 

    Lingula rectilateralis major, MCZ 145779            
   
MCZ 145779: 28mm long
           

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Lingula riciniformis Hall, 1847 – Description from Wilson, 1946

Lingula riciniformis Hall, 1847, p. 95, pl. 30, fig. 2; Winchell and Schuchert, 1893, p. 343, fig. 24, pl. 29, fig. 9; Wilson, 1946, p. 20, pl. 1, fig. 2.

Description: Shell is 6 mm to 8 mm in length. Has an even convexity and a somewhat attenuated posterior part ending in an obtuse beak.

Ecology: Infaunal burrowers and filter feeders.

 

    Lingula riciniformis, MCZ 145756            
   
MCZ 145756: 8mm long
           
    Lingula riciniformis, MCZ 145755            
   
MCZ 145755: 5mm long
           

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Leptobolus sp? - Description from Holmer and Popov, 2000

Description: Shell is small, elongate, and oval. Has ventral pseudointerarea with deep triangular pedicle groove. The ventral visceral area is thickened anteriorly, bisected by median ridge, and bifurcates near the anterior end. Dorsal visceral area has one to three low ridges.

Ecology: Infaunal burrowers and filter feeders.

 

    Leptobolus sp?, MCZ 145764            
   
MCZ 145764: 2mm long
           

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Schizocrania filosa Hall, 1847 – Description from Wilson, 1946

Orbivula ? filosa Hall, 1847, p. 99, pl. 30, fig. 9.
Schizocrania filosa Hall. Hall and Whitfield, 1875, p. 73, pl. 1, figs. 12-15; Hall and Clarke, 1892, p. 143, pl. 4, figs. 22-30; Bassler, 1915, p. 1144; Foerste, 1920, p. 202; Wilson, 1946, p. 23, pl. 2, figs. 17, 18; Cooper, 1956, p. 275, pl. 19, figs. 20, 21.

Description: Shell is subcircular in outline. The pedicle valve is flat or convex and apex is subcentral. Pedicle notch is deep and wide with its apical angle occupied by a plate. The brachial valve is larger than the pedicle valve and is convex with a terminal beak and two sets of muscle scars on the interior. One pair of strong posterior adductor scars are separated by a low median ridge, diverging from the beak and in some cases faintly divided transversly and a second pair of faint, minute scars are centrally placed. The surface of pedicle valve is concentrically wrinkled and the surface of the brachial valve is radially striated. Can be distinguished from other Ordovician brachiopods by the fine thread-like striae and the terminal beak on the brachial valve.

Ecology: Epifaunal, filter feeders that attach by cementation to some hard substrate. Substrate is often another organism’s shell. Schizocrania has been found cemented to conularids (Harland and Pickerill, 1987) and to orthoconic nautiloids (Lockley and Anita, 1980).

 

    Schizocrania filosa, MCZ 145782            
   
MCZ 145782: 8mm wide
           

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Trematis terminalis (Emmons, 1842) – Description from Wilson, 1946

Orbicula terminalis Emmons, 1842, p. 395, fig. 4.
Trematis terminalis (Emmons). Sharpe, 1848, p. 68, figs. 1-3; Emmons, 1855, p. 201, fig. 63, pl. 8, fig. 11; Wilson, 1946, p. 23, pl. 1, figs. 18a, b.

Description: Shell varies from 8.5 mm to 15 mm in length and from 10 to 13 mm in width. The brachial valve is gently convex with very fine concentric striae. Punctae penetrate the inner shell where they are comparatively distant and have a quincuncial rather than a radial arrangement. The punctae of the outer surface is in quincunx arrangement, but becoming crowded and out of either radial or concentric alinement near the anterior. This species differs from most other species in the quincuncial arrangement of the punctae.

Ecology: Epifaunal, filter feeders that attach by cementation to some hard substrate. Substrate is often another organism’s shell.

 

    Trematis terminalis, MCZ 145763            
   
MCZ 145763: 13 mm wide
           

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ORDER ACROTRETIDA

Conotreta rusti Walcott, 1889 – Description from Walcott, 1889

Conotreta rusti Walcott, 1889, p. 365, figs. 1-4; Hall and Clarke, 1892, p. 104, pl. 4, figs. 16-21; Cooper, 1956, p. 254, pl. 16, fig. 41.

Description: Larger or dorsal valve more or less acutely conical, rounded to subtriangular at the margin of the valve. The false area is nearly flat, narrow and grooved at the center by a longitudinal, narrow, shallow furrow. Surface of shell is marked by concentric growth lines that pass uninterruptedly over the false area. The cast of the interior of the conical valve show six narrow, elongate ridges radiating from the apex that separate five depressions on the sides and front of the shell. With this structure the interior of the shell would have five radiating ridges gradually widening out from the apex and becoming hollow towards their outer ends. The cast of the interior of the shell, near the apex, shows that one of the ridges joined a thicken portion of the shell, probably as the support for the siphonal tube.

 

    Conotreta rusti, MCZ 114284            
   
MCZ 114284: Syntype, 3.5 mm wide
           

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ORDER SIPHONOTRETIDA

Siphonotreta sp. deVerneuil, 1845 - Description from Holmer and Popov, 2000

Description: Shell is ventri- or equi-biconvex, elongate oval, and ornamented with undulating fila superposed on thick, widely spaced lamellae with closely spaced, evenly distributed short spines of uniform size. The foramen is circular and apical. Ventral pseudointerarea are large, apsacline, orthocline to anacline, undivided, and flattened, with concave median depression. The dorsal pseudointerarea are orthocline, shelflike, and fit closely into the median depression in ventral pseudointerarea. Median groove is wide, poorly defined, with propareas reduced. The visceral area of both valves is thickened and forms platforms. Internal pedicle tube long, possibly closed in adults, and emerges through the visceral platform, with a possible umbonal muscle scar. The dorsal anterior lateral muscle scars are placed between central muscle scars, and are bisected by a low median ridge.

 

    Siphonotreta sp., MCZ 145766            
   
MCZ 145766: 9.5mm wide
           

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SUBPHYLUM CRANIIFORMEA
CLAS CRANIATA
ORDER CRANIIDA

Crania trentonensis? Hall, 1866 – Description from Wilson, 1946

Crania trentonensis Hall, 1866, p. 12; Hall, 1872, p. 219, pl. 7, figs. 11, 12; Hall and Clarke, 1892, pl. 4, figs. 21, 22; Wilson, 1946, p. 26, pl. 2, fig. 10.

Description: Shell is small and subcircular with the posterior part slightly wider. The pedicle valve is flat, depressed convex or conforming to the host it attaches to, and lacks a pedicle opening. Brachial valve is convex, with the apex subcentral, and is posteriorly directed. The surface is smooth, spinose, and characterized by its strong concentric growth lines. Interior of both valves has two pairs of adductor scars, the posterior pair close to the margin and widely separated form one another, and the anterior pair smaller and near the center. The shell is calcareous and strongly punctate with the canals dividing near the surface.

Ecology: Epifaunal, filter feeders that cement by the entire surface of the ventral valve to a hard substrate. Substrate is often another organism’s shell.

 

    Crania trentonensis, MCZ 145765            
   
MCZ 145765: 6.5mm wide
           

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SUBPHYLUM RHYNCONELLIFORMEA
CLASS STROPHOMENATA
ORDER STROPHOMENIDA

Leptaena sp. Dalman, 1828 - Description from Cocks and Rong Jia-yu, 2000

Description: Shell outline is usually transverse and rounded anteriorly. The profile is concavoconvex with sharp anterior dorsal geniculation. Has a shell ornament of costellate to unequally parvicostellate. Concentric rugae are variable, but usually well developed. Has a small pseudodeltidium, a large chilidium and short dental plates. The ventral muscle field varies from subcircular to elongate with bounding ridges usually developed posterolaterally, sometimes curving round anteriorly. Cardinal process lobes are elongate and ventrally directed with socket ridges present, but usually weak, and sometimes with crenulations. The dorsal muscle field is variably impressed with median ridge often present and transmuscle ridges, diaphragm variably developed in dorsal valve.

Ecology: Epifaunal, filter feeders that attach to a hard substrate by a pedicle, which protrudes through the foramen in the ventral valve.

 

    Leptaena sp., MCZ 145770            
   
MCZ 145770: 11.5 mm hinge length
           

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Rafinesquina trentonensis (Conrad) – Description from Salmon, 1942

Leptaena alternata Conrad, 1838, p. 115; Hall, 1847, p. 102, pl. 31, fig. 1a-c, pl. 31A, figs. 1d-e.
Strophomena alternata Conrad, 1839, p. 63; Conrad, 1840, p. 201; Conrad, 1841, p. 37; Emmons, 1842, p. 395, fig. 3; Owen, 1844, p. 366, fig. 3; Emmons, 1855, p. 197, pl. 11, fig. 3, pl. 17, fig. 2; Billings, 1856, p. 204, fig. 3; Hitchcock, 1861, p. 293, fig. 199; Lesley, 1890, p. 1121, figs.
Orthis alternata Emmons, 1842, pp. 182, 319.
Orthis plana Castelnau, 1843, p. 38, pl. 14, fig. 1.
?Orthis huroniensis Castelnau, 1843, p. 37, pl. 14, fig. 6.
?Strophomena angulata? Owen, 1844, pl. 18, figs. 1, 3.
Leptaena trentonensis Conrad MS. Hall, 1847, p. 102.
Rafinesquina alternata (Conrad), Hall and Clarke, 1892, p. 282, pl. 8, figs. 6-11, 27, 28, pt. 2, 1895, pl. 84, figs. 17, 18; Winchell and Schuchert, 1893, p. 404, pl. 31, figs. 32-33, 34; Cumings, 1908, p. 926, pl. 37, fig. 1b;Wilson, 1946, p. 66, text-fig. 1, no. 3, pl. 5, fig. 4.
Rafinesquina trentonensis (Conrad). Salmon, 1942, p. 574, pl. 85, figs. 1-10; Cooper, 1956, p. 888, pl. 247B, figs. 5, 6, pl. 266 E, fig. 17; Rice, 1987, p. 158, pl. 4. fig. 9; Emerson, 2002, p. 362.

Description: Shell wider than long, broadly U-shaped in outline with greatest width at or near the hinge line. Cardinal angles are usually rectangular, but may show small ears or may be slightly obtuse. The lateral margins are usually straight and parallel. When the cardinal angles are auriculate, the lateral margins are faintly sinuate anterior to the ears. The anterolateral and anterior margins form a broad, smooth curve, varying only slightly from perfectly semicircular.

Ecology: Epifaunal, filter feeders that lie free on the soft substrate, possibly on a muddy sand or silt substratum.

 

    Rafinesquina trentonensis, MCZ 145769            
   
MCZ 145769: 30.5mm hinge length
           

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Sowerbyella curdvillensis (Foerste, 1912) – Description from Titus, 1992

Plectambonites curdsvillensis Foerste, 1912, p. 122, pl. 10, figs. 15a, 15b; Mather, 1917, p. 39, pl. 1, figs. 12, 13; Willard, 1928, p. 275-276.
Plectambonites punctostriatus Mather, 1917, p. 38-39, pl. 1, figs. 15-17.
Sowerbyella punctostriata (Mather, 1917). Wilson, 1946, p. 51, pl. 3, fig. 24; Cooper, 1956, p. 792-793, pl. 205C, figs. 9-25, pl. 206D, figs. 14, 15.
Sowebyella monilifera Cooper, 1956, p. 785, pl. 199A, figs. 1-8, pl. 206 E, figs. 16-28.
Sowerbyella curdsvillensis (Foerste, 1912). Cooper, 1956, p. 780-781, pl. 201A, figs. 1-13; Rice, 1987, p. 156, pl. 3, fig. 1; Titus, 1992, p. 769, figs. 4, 6; Emerson, 2002, p. 365, pl. 1, fig. 7.

Description: Adults are14 to 22 mm in width. Pedicle valve convexity shows medial fold or is flattened in some facies, rounded pedicle valves of low convexity found in all facies. Costellae are fine and straight with 3 to 4 fine ones between two coarser ones. Punctae are abundant and cardinal extremities are alate or rectangular in some facies. Rugae are rare on cardinal processes and pedicle interiors rarely seen. Brachial valve interiors are variable. Some forms are quite ornate with submedial septa, muscle scars, subperipheral thickening, and vascular markings while others are less well sculpted. The brachial exteriors display moderate concavity and simple, straight costellae.

Ecology: Epifaunal, filter feeders that lie free on the soft substrate, possibly on a muddy sand or silt substratum.

 

    Sowerbyella punctostriata, MCZ 145771            
   
MCZ 145771: 8.5mm hinge length
           

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Sowerbyella sericea (Sowerby, 1839) – Description from Wilson, 1946 and Bretsky, Flessa, and Bretsky, 1969

Leptaena sericea Sowerby, 1839, p. 636, pl. 19, figs. 1, 2.
Plectambonites sericeus (Sowerby, 1839). Hall and Clarke, 1892, pl. 15, figs. 15-19.
Sowerbyella sericea (Sowerby, 1839). Jones, 1928, p. 414, pl. 21, figs. 1-4; Wilson, 1946, p. 51, pl. 3, fig. 26.

Description: Shell is medium size, wider than longer, and gently to strongly concavo-convex. Outline is subquadrate or semicircular and cardinal angles are slightly acute. There are fine, primary, secondary, and tertiary striae, differentiated in size on the pedicle valve, but more equal on the brachial valve. A few wrinkles are present along the hinge line in some cases. The pedicle valve interior has well-defined dental lamellae, two elongate-oval muscle scars extending halfway to the anterior and a median septum 2 mm to 3 mm in length with prongs at right angle to one another forming the inner side of the muscle scar. The brachial valve has short divergent crural plates, two prominent subparallel septa originating just anterior to the cardinal process and forming the inner side of the muscle scar.

Ecology: Epifaunal, filter feeders that lie free on the soft substrate, possibly on a muddy sand or silt substratum.

 

    Sowerbyella sericea, MCZ 145768            
   
MCZ 145768: 20mm hinge length
           

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CLASS RHYNCHONELLATA
ORDER ORTHIDA
SUBORDER ORTHIDINA

Dalmanella testudinaria (Dalman, 1828) – Description from Williams and Wright, 1963

Orthis testudinaria Dalman, 1828, p. 115, pl. 2, figs. 4a-e.
Dalmanella testudinaria (Dalman, 1828). Williams and Wright, 1963, p. 29, pl. 2, figs. 7, 8, 11-13, 16-19; Temple, 1965, p. 383, pl. 3, figs. 1-7, pl. 4, figs. 1-6, pl. 5, figs. 1-7, pl. 6, figs. 1-7; Bergström, 1968, p. 8, pl. 2, fig. 5; Havlíček, 1977, p. 137, pl. 32, figs. 1-15, 18, 19, 23, pl. 56, fig. 13; Nikitin in Appollonov et al., 1980, p. 38, pl. 12, figs. 1-17; Cocks, 1982, p. 760, pl. 79, figs. 4-12.

Description: Shell is ventri-biconvex, subciruclar with a sulcate brachial valve. Shell ornamentation is costellate with 3 ribs per mm at a distance of 5 mm anterior to the dorsal beak. Cardinal process has an undifferentiated bilobed myophore and a shaft anteriorly merging into the median ridge. Fulcral plates and crural pits are present.

Ecology: Epifaunal, filter feeders that attach to a soft substrate (muddy sand or silt substratum) by a pedicle, which protrudes through the foramen in the ventral valve.

 

    Orthis testudinaria, MCZ 145773            
   
MCZ 145773: 8mm hinge length
           

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Orthis sp. Dalman, 1828 - Description from Williams and Harper, 2000

Description: Shell is large, planoconvex to weakly concavoconvex, rectimarginate, costate, and capillate. The ventral muscle scar is suboval. Brachiophores are widely divergent rods and the ventral vascula media parallel proximally.

Ecology: Epifaunal, filter feeders that attach to a soft substrate (muddy sand or silt substratum) by a pedicle, which protrudes through the foramen in the ventral valve.

 

    Orthis sp., MCZ 145775            
   
MCZ 145775: 17mm hinge length
           
    Orthis sp., MCZ 145776            
   
MCZ 145776: 16mm hinge length
           

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Platystrophia amoena McEwan, 1919 - Description from Raymond, 1921

Platystrophia amoena McEwan, 1919, p. 412, pl. 43, figs. 1-8; Raymond, 1921, p. 17, pl. 6, figs. 1-5, 11; Wilson, 1946, p. 32, pl. 3, figs. 7a, b;; Emerson, 2002, p. 396, pl. 3, fig. 1.

Description: Shell below the average size for the genus, the valves moderately and subequally convex, the plications not coarse, and especially at the sides, rather sharp; those on the fold often more broadly rounded. The greatest width is at the hinge, the cardinal angles usually projecting a little even in old specimens. The sinus is shallow, flat-bottomed, or slightly concave, the fold very slightly elevated and with a gently convex or flat crest. The great majority of specimens have three plications in the sinus and four on the fold. The median plication in the sinus is often noticeably stronger than the others, and there is a corresponding median furrow on the fold separating the two pairs of plications. There may be as many as six plications in the sinus and seven on the fold, but such specimens are unusual. The number on each side of the fold and sinus is variable. There may be from seven to ten on the brachial and eight to eleven on the pedicle valve; nine on one valve and ten on the other seems the most common number.

Ecology: Epifaunal, filter feeders that attach to a hard or soft substrate by a pedicle, which protrudes through the foramen in the ventral valve.

 

      Platystrophia amoena, MCZ 144883              
     
MCZ 144883: Hypotype, 17mm wide
             
      Platystrophia amoena, MCZ 144884              
     
MCZ 144884: Hypotype, 20mm wide
             

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  Platystrophia biforata Schlotheim

Description: Considered to be a synonym of Platystrophia amoena (Wilson, 1946 and Cooper, 1956).

Ecology: Same ecology as Platystrophia amoena.

 

      Platystrophia biforata, MCZ 145780            
     
MCZ 145780: 15mm hinge length
           
  Platystrophia biforata var. lynx Eichwald

Description: Considered to be a synonym of Platystrophia amoena (Wilson, 1946 and Cooper, 1956).

Ecology: Same ecology as Platystrophia amoena.

 

      Platystrophia biforatus var. lynx, MCZ 145772            
     
MCZ 145772: 20mm hinge length
           

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ORDER RHYNCHONELLIDA

  Rhynchonella capase - Description of Genus from Owen and Manceñido, 2002

Description: Shell is small to medium in size, subtriangular, gibbous, and nearly convexiplane and cynocephalous. Has a high dorsal fold, and a ventral sulcus that is somewhat flattened. Costae are few and sharp anteriorly. Commissure is uniplicate and acuminate to paucidentate. The beak is small and slight incurved. Dental plates are strong, septalium is shallow, and the dorsal median septum is short. Crura are short and raduliform.

Ecology: Epifaunal, filter feeders that attach to a hard substrate by a pedicle, which protrudes through the foramen in the ventral valve.


      Rhynchonella capase, MCZ 145781            
     
MCZ 145781: 8.5mm long
           

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ORDER ATRYPIDA
SUBORDER ANAZYGIDINA

Anazyga recurvirostra (Hall, 1847) – Description from Copper, 1977

Atrypa recurvirostra Hall, 1847, p. 140, pl. 33, fig. 5a-d.
Anazyga recurvirostra (Hall, 1847). Copper, 1977, p. 306, pl. 37, figs. 11-15, text-figs. 5-6.

Description: Shell is small (5 to 7 mm wide), longer than wide, strongly biconvex to ventribiconvex with hypercline beaks. Ribs are fine and evenly sized throughout, though slightly larger flanking the sulcus, averaging about twenty-four in number. Brachial valve is somewhat flattened anteriorly and very faintly sulcate. The pedicle valve is more arched with weak anterior fold. Internally, the pedicle valve is thickened apically with faint median septum, not pedicle constrictions, deltidial plate minute, solid, pointed dorsally, dental cavities elongate, teeth simple, dorso-median projections supported terminally by dorsal wall. The brachial valve has sturdy, short socket plates separated medially by a pit without cardinal process. Crura are extened from small round bases located on inner side of socket plates, diverging laterally at about a 45 degree angle to the mid-shell, then curving inwardly, with spiral whorls beginning at anterior-most portion. Jugum in broad V-shaped band joined anterior to spiralial apex. Two to three spiral whorls present with axes directed medially.

Ecology: Epifaunal, filter feeders that attach to a hard substrate by a pedicle, which protrudes through the foramen in the ventral valve.

 

    Anazyga recurvirostra, MCZ 145774            
   
MCZ 145774: 5mm hinge length
           
    Anazyga recurvirostra, MCZ 145778            
   
MCZ 145778: 4.5mm long
           

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Zygospira modesta (Say in Hall, 1847) – Description from Copper, 1977

Atrypa modesta Say in Hall, 1847 pp. 141-142, pl. 33, fig. 15.
Zygospira modesta (Say in Hall). Copper, 1977, p. 303, pl. 37. figs. 1-8, text-figs. 3-4.

Description: Shell moderately sized, wider than long, and planoconvex to weakly biconvex with 15-18 ribs over all. Has 4 strong mid-ribs on the pedicle valve, and 3 corresponding mid-ribs on the brachial valve and the remaining lateral ribs decreasing in size posteriorly. Average width is 8.1 mm, length is 7.2 mm, and depth is 3.9 mm. Internally shell is thin and weak, irregular pedicle collar structures line pedicle cavity. The dental cavities are distinct with teeth near horizontal in the sockets. Has small nodular crural bases on inner socket ridges, crura diverge widely to sides, jugum arising at or near position of cone axes, initially curving postero-medially dorsal to the spiralia, then straightening medially and curving dorso-anteriorly to fuse. Spiralia are D-shaped with straight sides forming a weak V (open anteriorly). No cardinal process observed and dorsal septum is strong. Muscle scars are weakly impressed and poorly known.

Ecology: Epifaunal, filter feeders that attach to a hard substrate by a pedicle, which protrudes through the foramen in the ventral valve. Zygospira modesta has been found attached in clusters by pedicles to stems of crinoids, such as Pycnocrinus (Sandy, 1996). It has also been found attached to bryozoans.

 

    Zygospira modesta, MCZ 145777            
   
MCZ 145777: 8.5mm long
           

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