292 ANOMIID^. 



Pernopecten agrees with Amussiura in its subsymmetrical ears, 

 cardinal cartilage-pit, and in the absence of radiating ridges, 

 but differs in its straight hinge-line and lateral cartilage-pits. 

 Entolium, Meek, is founded on a Jurassic species from California, 

 P. aurarium, Meek, 



CRENiPECTEN, Hall, 1883. Like Aviculopecten in form; hinge 

 furnished with a series of small cartilage-pits throughout its 

 entire length. 12 sp. Chemung Group; N. Y. F. Leon, Hall. 



Streblopteria, M'Coy, 1851. 



Distr. — Carboniferous. 8. laevigata, M'Co}^ (cxxxii, 9). 



Shell ovate or rounded, obliquely extended towards the ante- 

 rior side; posterior wing broad, undefined, nearly rectangular, 

 extending nearly as far as the posterior margin of the shell ; 

 anterior ear small, deeply defined ; surface smooth or radia- 

 tingly ridged ; one large, faintly marked muscular impression a 

 little behind the middle ; one short, narrow tooth, slightly 

 diverging from the hinge-line, on the posterior side of the beaks ; 

 ligament confined to a narrow, simple facet on the hinge-margin. 



These shells diff'er from the short-winged Aviculse, to which 

 they are most allied, by the obliquity of the body of the shell 

 being towards the anterior instead of the posterior side. 



{Anomiacea.) 



Family ANOMIIDiE. 



Shell thin, perlaceous, with a deep notch or hole in the inferior 

 valve near the beaks, for the passage of a byssal plug, by which 

 the shell is attached. 



Mouth with narrow, plain lips, confluent with the gills, palps 

 obsolete ; mantle quite open, except at the hinge, with a double 

 pendent margin, fi-inged with short cirri ; no ocelli ; gills two on 

 each side, unsymmetrical, united posteriorly, and suspended by 

 two falciform membranes ; outer gill-lamina furnished with a 

 broad reflexed margin ; foot small, cylindrical, expanded at the 

 end and grooved. Sexes distinct. Byssus large, laminar, 

 passing through a nearly complete foramen in the right mantle- 

 lobe, and attached by a powerful muscle to the centre of the 

 left valve. The Anomia ephippium is used in France as an 

 article of food. 



Anomia, Linn., 1T6Y. 



Etym. — Anomios, unequal. 



Syn. — Fenestrella, Bolten. Cepa, Humph. 



Distr. — 20 sp. North America, Britain, Black Sea, India, 

 Australia, West America, Icy Sea. Low-water — 100 fathoms. 

 Fossil, 36 sp. Oolite — ; Chili, United States, Europe, India. 

 A. ephippium, Linn, (cxxxiii, 24). 



