No. 109.] 127 



Spirifer gregaria. 



Spirifer gregaria, Dr. Clapp in MSS. 

 Pal. N.Y. Vol.iv. 



Shell irregularly subglobose, longitudinally or transversely a 

 little oval ; hinge equalling the greatest width of the shell, an- 

 gular or slightly rounded : dorsal valve the smaller, somewhat 

 semicircular, length about two-thirds the width, rising along 

 the middle into a prominent mesial fold, on each side of which 

 there are five to nine simple rounded plications ; mesial eleva- 

 tion slightly flattened, or marked with a faint longitudinal de- 

 pressed line ; beak rising a little above the hinge, more or less 

 incurved : ventral valve subquadrilateral, having a distinct 

 subangular sinus extending from the beak to the front, where it 

 terminates in a short subtriangular projection (fitting into a 

 corresponding depression in the front of the opposite valve) ; 

 on each side of the sinus, there are about six to ten rounded 

 plications ; beak rising far above the hinge, extremely gibbous 

 and strongly incurved ; foramen somewhat narrow triangular ; 

 area rather broad, sublinear, extending to the extremities of the 

 hinge line, distinctly arcuate. Surface ornamented by regular 

 subimbricating zigzag lamellse or lines of growth. 

 Geological position and locality. In the limestone of the Upper Hel- 

 derberg, rarely in Eastern New- York : common in G-enesee and Erie 

 counties, and in Ohio and Kentucky, in the same geological position. 



Spirifer grieri (n. sO- 

 Pai. n.y. Voi.iv. 



Shell transversely oval or subrhomboidal ; length about five- 

 sixths the breadth; valves nearly equal, more or less gibbous; 

 hinge less than the greatest width of the shell, rounded at the 

 extremities : dorsal valve with a prominent angular mesial 

 fold extending from the beak to the front, marked with indistinct 

 plications, about three originating near the beak and bifurcating 

 once or twice before reacliing the front, having on each side 

 about nine rounded simple plications ; beak rising a little above 



