38 
PALAEONTOLOGY OF NEW-YOKK. 
The cast of the ventral valve is depressed-convex above, depressed along 
the centre below, with a median groove from the adductor scar nearly 
to the front of the shell. Muscular impression elliptical, occupying less 
than half the length of the valve, and about one-third the width : 
lower half of valve marked by strong vascular impressions. 
Two specimens in the State Collection, having respectively the length of about 
one-half and five-eighths of an inch, are referred with hesitation to this species. 
The cast of the ventral valve possesses characters which distinguish it from any 
species of which I know the interior. It is possible that these may he the young 
of 0. livia, of which I do not know the interior at this time. 
Geological formation and locality. In the Schoharie grit; in Albany and Schoharie 
counties, N.Y. 
Orthis livia. 
PLATE Y. 
Orthis livia [? ] Billings, Canadian Journal of Industry, Science and Art, No. xxvii, p. 269, 1860. 
A single well-preserved specimen, measuring one inch and one-tenth 
in length by one inch and two-tenths in width across the middle, presents 
the following characters : 
Shell suborbicular, front and sides rounded : cardinal line and area equal¬ 
ling nearly half the width of the shell; cardinal extremities rounded. 
Dorsal valve of medium convexity, most convex above the middle, and 
curving gently and evenly towards the front and lower lateral margins, 
more abruptly sloping and scarcely concave towards the cardinal ex¬ 
tremities ; without perceptible mesial fold or depression : dorsal area 
small, flat or lying in the plane of the margins of the valve, about one- 
half as wide as the ventral area; dorsal beak projecting slightly beyond 
the edge of the area, but not incurved. Yentral valve moderately con¬ 
vex, the greatest convexity about one-third the length from the beak, 
flattened or depressed below, and slightly concave towards the front 
and sides : ventral area of moderate size, inclined backwards; ventral 
beak neatly defined, incurved, and projecting slightly beyond the area 
line. 
