No, 109.] 



4^5 



tte width of tlie shell ; area broad, flat, sometimes nearly on a 

 plane with the greater diameter of the shell ; foramen closed. 

 Surface marked by prominent rounded striae, which increase by 

 implantation, and are crossed at intervals by distinct subimbri- 

 cating concentric lines of growth. 



Ttis shell has much the general habit of O.Hmhraculum of the Car- 

 'boniferous system, but is not resupinate. 



Orthis MULTISTRIATA ;( n. S.). 



Pal. N.Y. Vol. iii, pi. 15, f. 2. 



Shell circular or transversely suboval : ventral valve most convex 

 near the beak, depressed so as to form a broad shallow undefined 

 sinus, which sometimes gives to the front a subemarginate 

 aspect ; beak a little more prominent than the opposite, slightly 

 incurved : dorsal valve more elevated, most convex between the 

 middle and the beak ; beak rising above the hinge, obtuse and 

 incurved • hinge-line straight, about half the width of the shell ; 

 area small ; foramen narrow, extending nearly to the apex. 

 Surface marked by fine, crowded, nearly equal striae, which 

 increase chiefly by implantation, and are* crossed by a few faint 

 concentric lines of growth. 



Closely related to the ventricose varieties of Orthis resiipinala, and also 

 to the Orthis striatula of D'Orbigny. 



OSTHIS MULTISTRIATA. 



