60 [ Senate 



beak closely incurved : liinge-line slightly declinirig on each 



side of the centre, and rounded at the extremities ; area narrow, 



strongly striated longitudinally. Surface marked by numerous 



fine strige which bifurcate once or oftener between the beak and 



base of the shell, concentrically crossed by imbricating lamellae. 



The species is distinguished by its rounded extremities and numerous 



fine striae, which bifurcate or increase by interstitial addition, chiefly near 



the middle of the shell, but often near the beak and base. A few of the 



striae (six or eight) near the beaks are much stronger than the others. 



Geological position and locality. Shaly limestone of the Lower Hel- 

 derberg, Albany and Schoharie counties. 



Spirifer? perforatus (n. s.). 



Pal. N.Y. Vol. iii, pi. 27. 



Shell somewhat semicircular, with the hinge extremities rounded ; 

 hinge-line slightly curved ; area very small : ventral and dorsal 

 valves nearly equally convex ; beak of the ventral valve slight- 

 ly incurved and perforate at the extremity j dorsal valve with 

 the beak strongly incurved, and filling the foramen of the op- 

 posite valve. Entire surface marked by sharp radiating striae, 

 which bifurcate once or twice before reaching the base, so as to 

 present fascicles of two or three on the centre of the shell. 

 Geological position and locality. Shaly limestone of the Lower Hel- 



derberg group, Albany county and Hudson. 



Spirifer concinna ( n. s.). 



Pal. N.Y. Vol. iii, pi. 25, f. 2. 



Shell semicircular or semielliptical ; extremities rounded ; valves 

 almost equally convex : ventral valve gibbous towards the 

 beak ; beak more or less elevated above the hinge-line, and 

 abruptly incurved at the apex ; mesial sinus subangular, and 

 produced into an angular extension which is much elevated, and 

 sometimes slightly incurved in front : dorsal valve very convex 



