45© 
PALAEONTOLOGY OF NEW-YORK. 
PLATE CVI. 
Fig. 1 a, b, c, d. Dorsal, ventral and profile views of this species. (The figures, unfortunate¬ 
ly, represent too many plications by two on each side of the centre.) 
Fig. 1 e. The interior of the dorsal valve, showing the cardinal process, etc. 
Fig. If A cast or impression of a larger dorsal valve. 
The preceding, with a few specimens in similar condition, are all that I have been 
able to obtain from the Oriskany sandstone in New-York- 
The following illustrations have been made from a study of the Maryland col¬ 
lections at a later period : 
PLATE CIII B. 
Fig. 1 a, b. Ventral and dorsal views of a specimen of this species. 
Fig. 1 c, d. Profile view of a specimen of the ordinary form of this species. 
Fig. 1 c. Interior of specimen with rounded extremities. 
Fig. If. Interior of the dorsal valve of this species. 
Geological position and locality. In the Oriskany sandstone : Albany, Schoharie, 
Greene and Ulster counties (New-York); Cumberland (Maryland), and in Virginia 
and Canada. 
leptocoelia fimbriata (n. s.). 
Plate CIII B. Fig. 2 a -/. 
Shell small, longitudinally semielliptical, the length less than the width. 
Ventral valve convex, more elevated along the middle, declining re¬ 
gularly at the sides, the cardinal angles somewhat compressed : beak 
small, little elevated above the cardinal line and slightly incurved, with 
a minute rounded foramen at the extremity, the low r er side of which, 
when entire, is completed by two small deltidial pieces. Dorsal valve 
flat or slightly convex, the front and lower lateral margins abruptly 
inflected : beak straight; hinge-line of the ventral valve more de¬ 
clining, with border often grooved for the reception of the edge of the 
dorsal valve. The hinge-line of closed valves often ornamented by 
fibres or fimbria, forming a byssus-like appendage. 
Surface marked by about eleven or twelve rounded or subangular plica¬ 
tions on each valve, two of which, in the middle of the ventral valve, 
are more prominent and slightly larger than the others ; and between 
