Sg PALEONTOLOGY OF NEW- YORK. 



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 spociinens 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 be the young 



of O. 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 liria. 



•PLATE V. 

 Ort\ii livia [? ] Billihos, 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. Ventral 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. 



