44 [ Senate 



Orthis perelegans ( n. s.). 



Pal. N.Y. Vol. iii, pi. 13. 



Shell transversely oval ; valves nearly equally convex : ventral 

 valve elevated along the middle from the beak towards the front, 

 and sloping laterally ; beak small, pointed, incurved, extending 

 little beyond the other : dorsal valve subventricose, more or 

 less depressed along the middle from near the beak to the front ; 

 beak small, not much elevated above the hinge-line i cardinal 

 margin generally sloping a little from the beaks, rounding im- 

 perceptibly into the lateral margins , area narrow, nearly half 

 the width of the shell ; foramen broad triangular, extending 

 nearly to the apex of the beak. Surface marked by fine, ir- 

 regular, bifurcating, longitudinal strise, crossed by concentric 

 lines of growth. 



Chiefly distinguished from the last by its more ventricose dorsal valve, 

 and by the hinge-line sloping more from the beaks laterally ; but more 

 leadily distingui&hcd by the internal differences. 



Oethis perelegans. 



Orthis deformis ( n. s.)' 



Pal. NT. Vol. iii, pi. 14, f. 3. 



Shell suborbicular, lenticular : ventral valve more convex than 

 the opposite, most elevated between the centre and beak ; beak 

 straight, often distorted in consequence of having been the point 

 by which the shell was attached : dorsal valve depressed- convex, 

 most elevated near the beak ; beak not extending beyond the 

 binge-line ; hinge-line straight, equalling about three-fourths 



