20 PALEONTOLOGY OF NEW -YORK. 



30. 3. LEPTiENA FASCIATA (n. s/).)- 



Pl. IV. (bit). Figs. 3 a, b, c. 

 Semi-elliptical, wider than long; surface marked by prominent sharp strise, between 

 which are fascicles of three or four smaller ones ; striae dichotomous, and increasing to- 

 wards the margin. 



This shell presents many of the essential features of i. interstrialis upon the external 

 surface, but I am inclined to believe that a complete exposure of all the parts would prove 

 it a distinct species. It differs from the young of that shell, in its more convex form and 

 broader proportions ; while the fascicles of striee are remarkably distinct, but not crenulated, 

 aa in good specimens of L. interstrialis. 



Fig. 3 a, b. Convex valves of two individuals. 

 Fig. Be. A larger specimen of the same. 



Position and locality. In the thinbedded portions of the Chazy limestone, upper part of 

 the mass, near Chazy village, Clinton county. The specimen, fig. 3 c, is a larger in- 

 dividual, apparently identical with this species, from Galway, Saratoga county, in the 

 concretionary or brecciated portion of the rock. {State Collection.) 



31. 1. ORTHIS COSTALIS («. *p.). 



Pl. IV. (bi8). Figs. 4 a, b. 



Dorsal valve very convex, subconical, sloping rapidly towards the margin ; ventral valve 

 flat ; surface marked by about 32 distinct strong rounded radii, which are continuous, and 

 enlarging towards the margin ; dorsal area large, triangular ; beak short, not incurved ; 

 cardinal line nearly equal to the width of the shell. 



The strong rounded undivided costaeupon the surface, of each valve distinguish this from 

 any other species in the lower strata, though there is a larger species in the Trenton lime- 

 stone which has sometimes undivided radii. The visceral impression under the beak of the 

 dorsal valve is narrow, somewhat tripartite at the base, and margined by a sharp ridge. 

 Cast of the dorsal valve convex, strongly marked near the margin by impressions of the 

 radii. 



This shell resembles in general form 0. testudinaria of the Trenton limestone, but is 

 more convex above, the striae coarser and less numerous, and the beak is shorter and not 

 incurved. The casts are likewise equally distinct. 



Fig. 4 a. An imperfect shell, showing the radii towards the margin. 



Fig. 4 6. A cast showing the visoeral marking, and casts of radii near the base of the shell. 

 Fig. 4 e. An impression of the convex valve, smaller than the other specimens. Such impressions are 

 abundant. 



Position and locality. In the thinbedded upper portion of the Chazy limestone, associated 

 with all the other brachiopods of the mass. Chazy village, Clinton county. (State Collection.) 



