ORISKANY SANDSTONE. 
449 
Leptocoelia flabellites. 
Plate CVI. Fig. 1 a—f\ and Plate CIII B. Fig. 1 a-f. 
Mrypa flabellites : Conrad, Annual Report on the Palaeontology of New-York for 1841, p.55. 
Leptoccelia propria* : Hall, Regents’ Report of 1856, p. 108; Palaeozoic Fossils, 1857, p. 68. 
Shell somewhat semielliptical, varying to suborbicular or transversely 
oval, generally broader than long. Ventral valve convex, most promi¬ 
nent along the middle, declining laterally : beak incurved, with a small 
round perforation in the extremity, which is completed on the lower 
side by the two deltidial pieces ; or, in the absence of these, the fora¬ 
men is completed by the umbo of the dorsal valve. Dorsal valve flat : 
beak straight; hinge sloping from the beaks at an angle of 110° to 160°, 
rounded at the extremities. 
Surface marked by ten to fourteen simple angular plications ; two of 
which, on the middle of the ventral valve, are a little larger and slight¬ 
ly more prominent than the others ; and, between these, there is a third 
smaller depressed plication, forming an indistinct sinus. On the dorsal 
valve the two middle plications are a little closer together, and slightly 
more prominent near the fronf, than the others; while the depressions 
separating them from these, each side, are a little wider and deeper 
than those between the other plications. 
This species presents some varieties of form, apparently due to age and other in¬ 
fluences; the hinge-line of some individuals being often more extended and more 
nearly straight. The extension of the beak varies in different individuals, and in 
those from different localities. The silicified condition of the specimens has obscured 
the finer surface markings. Many of the specimens appear to retain remains of fine 
radiating striae; while more distinct concentric lines, and occasional stronger un¬ 
dulations of growth, are visible in most of them. 
In specimens from New-York, Maryland and Canada, which I have referred to 
this species, there are some slight differences which appear to be due to the condition 
of the sediments in the different localities. 
* I had overlooked the description of Mr. Conrad of A. JIablelites. as designating this species, at the 
time I published the descriptions of new palseozoic fossils; and it is only as these pages are going through 
the press that my attention lias been directed to the subject, leaving no doubt of the identity of the species. 
[ Palaeontology III.] 57 . 
