292 ANOMIIDA. 
Pernopecten agrees with Amussium in its subsymmetrical ears, 
cardinal cartilage- -pit, and in. the absence of radiating ridges, 
but differs in its str: ight hinge-line and lateral cartilas “e- pits. 
Entolium, Meek, is founded on a Jurassic species from Califor nia, 
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. P. Leon, Hall. 
STREBLOPTERIA, M’Coy, 1851. 
Distr.—Carboniferous.  S. epubgeb: M’Coy. (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 ane 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 differ from the short-winged Aviculz, 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.) 
Famity ANOMIIDA. 
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 sheli 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, fringed with short cirri; no ocelli ; ; gills two on 
each side, unsymmetrical, united posteriorly , and suspended by 
two faleiform 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., 1767. 
EHtym.—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. (exxxiii, 24). 
