LAMEIJJBRANCHIATA. 53 



Lyriopecten anomi^formis. 

 plate iv, fig. 10 ; plate x, fig. 5 ; and plate lxxxii, fig. 2. 



Lyriopecten mwtmwformis. Hail. MSS. foi- vol. v, pt. 1. 1877. 



" " " Catalogue Amer. Palaeozoic Fossils, S. A. Miller. 1877. 



" " P'l'- N. Y., vol. V, lit. 1. Plates and Explanations ; PI. 4, tig. 10 ; pi. 10, 



tifr. ^. 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 striaj. The ears show the same surfiice markings. 



Cartilage-pit small. Ijigamental 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. 



