LAMELLIBRANCHIA TA. 
53 
Lyriopecten anomijeformis. 
FLATE IV, FIG. 10; PLATE X, FIG. 5; AND PLATE LXXXII, FIG. 2. 
Lyriopecten anomiwformis, Hall. MSS. for vol. v, pt. 1. 1877. 
“ “ Catalogue Amer. Palaeozoic Fossils, S. A. Millki;. 1877. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 4, fig. 10; pi. 10, 
fig. 5. Jan., 1883. 
Shell larger than medium size, obliquely elliptical or obovate; height nearly 
equal to the length; the transverse axis makes an angle of about 45° with 
the hinge-line; margins regularly rounded anteriorly and along the base, 
becoming obscurely truncated on the upper postero-lateral portion of the 
shell. 
Left valve slightly convex. Right valve nearly flat. 
Hinge-line straight, anterior; length equal to one-half the transverse 
diameter of the shell. 
Beak of left valve obtuse, rounded, oblique, not well-defined, situated 
anterior to the middle of the hinge, and extending to the hinge-margin, but 
not rising above it. Beak of right valve scarcely defined. 
Anterior ear small, obscure, only indicated by the short portion of the 
ligamental area anterior to the beak. Posterior ear undefined, triangular; 
margin straight; extremity obtuse. Byssal sinus in the left valve a small 
notch; in the right valve a very deep, elliptical sinus. 
Test thin, marked on the left valve by numerous fine, thread-like radii, 
of which every fourth to eighth one is much stronger than the intermediate 
lines, crossed by fine striae of growth; the larger rays are about 20 in 
number. On the right valve the radii are represented by obscure, undu¬ 
lating, unequal striae. The ears show the same surface markings. 
Cartilage-pit small. Ligamental area thickened, with about eight flat, 
longitudinal lines extending to the extremities of the hinge. 
A left valve measures 62 mm. from the anterior ear to the postero-basal 
margin; from the extremity of the beak the height is 55 mm., and the 
length, parallel to the hinge, is about 54 mm.; hinge-line 27 mm. 
