154 [Senate 



SpIRIFER MACJIA. 

 Pal. N.Y. Vol. iv. 



Shell transverse : ventral valve presenting a subquadrangular 

 outline ; hinge-line greatly extended, terminating in mucronate 

 points ; sides nearly straight and sloping abruptly to the mesial 

 sinus in front, the beak much elevated : dorsal valve smaller, 

 somewhat semicircular, convex in the middle, flattened or con- 

 cave towards the extremities, having a narrow abruptly elevated 

 mesial fold, on each side of which there are about six or seven 

 simple plications ; beak scarcely incurved or elevated above 

 the hinge-line : ventral valve most prominent near the umbo, 

 having a narrow and very distinct mesial sinus terminating in a 

 short round projection in front ; plications about seven or eight 

 on either side, those bounding the sinus very prominent ; beak 

 and upper part of the area arcuate, and projecting beyond the 

 cardinal margin of the opposite valve ; area moderate, and 

 sloping gradually from the beaks to the cardinal extremities. 

 Surface markings unknown. 

 Geological 'position and locality. In the limestones of the Upper Hel- 



derberg group, Erie county. 



. Spirifer DISPARILIS. 

 Pal. N.Y. Vol.iv. 



Shell small, semicircular, length more than half the width ; hinge 

 a little less than the greatest breadth of the shell, rounded at 

 the extremities ; dorsal valve much the more depressed, marked 

 by five or six broad rounded plications, the middle one smaller 

 than those contiguous, and separated from them on each side 

 by a larger depression than those between the others; beak 

 scarcely incurved : ventral valve much the more convex, most 

 prominent at the umbo, marked by about five large plications, 

 of which one on each side of the sinus is larger and more ele- 

 vated ; beak arcuate ; area moderate, sloping from the beaks to 

 the lateral extremities ; foramen conspicuous. Surface unknown. 

 Geological position and locality. In limestones of the Upper Helder- 



berg group, Erie county. 



