140 
PALAEONTOLOGY OF NEW-YORK. 
177. 10. ATRYPA DEFLECTA ( n. sp.). 
Pl. XXXIII. Figs. 4 a, b. 
Sub-planoconvex, with the margins compressed, and deflected towards the front; length 
and breadth about equal; cardinal line somewhat extended, curved ; dorsal valve with a 
prominent ridge along the middle; beak extended, prominent, incurved ; ventral valve 
depressed-convex, with a mesial sinus ; surface with about 20 small regular radiating striaj, 
which are rarely divided towards the margin. 
A few specimens only of this shell have been found ; in these, the form is constant, as 
represented in the figure ; but the markings and general aspect approximate it to the next 
species. 
Fig. 4 a. View of dorsal valve, b. Front view, showing the form of the two valves. 
Position and locality. Near Martinsburgh, Lewis county, in the central part of the 
Trenton limestone. 
178. 11. ATRYPA RECURVIROSTRA {n. sp.). 
Pl. XXXIII. Figs. 5 a, b, c, d. 
Elliptical, somewhat ovoid, very symmetrical ; breadth one fourth of an inch, length a 
little greater ; dorsal valve with the middle elevated, regularly convex on the sides, the 
beak extended and gracefully incurved over the beak of the ventral valve, which is re¬ 
gularly convex, with a slight longitudinal depression ; surface of each valve marked by 
about 24 regular simple longitudinal striae, which continue entirely to the beak. 
The preceding species approximates to this one in general form and character of strim ; 
but the sides are more expanded, and the shell has a distinct mesial sinus and elevation. 
These characters usually increase with the age of a shell; and since the form of the one 
under consideration is very constant in a large number of specimens, which are of nearly 
uniform size, and smaller than the one figured, we may presume that it is a distinct species. 
It will be readily recognized by its rotund symmetrical form, which is more elongated, and 
more finely and evenly striated than any other species in the rock, except the preceding 
one. 
Fig. 5 a. Dorsal valve. 
Fig. 5 b . Profile view. 
Fig. 5 c. Cardinal view, showing the incurved beak of the dorsal valve. 
Fig. 5 d. Ventral valve separated from the dorsal. This valve is nearly circular, the beak being scarcely 
extended beyond the cardinal margin. 
Position and locality. This shell occurs in considerable numbers in a compact greyish 
blue bed of limestone near the centre of the Trenton limestone, near Martinsburgh, Lewis 
county. It has also been seen at Lowville and at Middleville. [State Collection.) 
