No. 109.] 129 



A single specimen of this species, from Columbus, Ohio, is mucli ex- 

 foliated ; the plications are more rounded, and the mesial fold less de- 

 pressed in the centre, than in specimens of similar general character from 

 New- York. The species has doubtless been originally marked by fine ra- 

 diating strias and concentric lines of growth. 



In many respects this shell resembles S. eurutincs of Owen, but has a 

 greater convexity of the dorsal valve, with beak more prominent and in- 

 curved ; and it likewise has a narrower foramen, and only about half the 

 number of plications of that species. 



Geological position and Incalitij. Upper Helderberg limestone of Wes- 

 tern New- York ? and near Columbus, Ohio. Dr. Mann. 



Spirifer oweni ( n. s.). 



Pal. N.y. Vol. iv. 



Shell transversely oval, moderately gibbous j length about three- 

 fourths the breadth ; valves nearly equal ; hinge nearly or quite 

 equal to the greatest width of the shell, angular or a little 

 rounded at the extremities ; front nearly straight, sometimes a 

 little concave at the termination of the sinus : dorsal valve 

 transversely oblong, somewhat semicircular, having a smoothly 

 rounded mesial fold marked by a longitudinal depression down 

 the middle, sloping gently to the anterior and lateral margins, 

 but flattened a little near the extremities of the hinge, having 

 on each side of the mesial elevation about fifteen simple sub- 

 angular plications ; beak rising somewhat above the hinge-line, 

 incurved ; area incurved : ventral valve most prominent near 

 the umbo, having sixteen or seventeen plications on each side ; 

 mesial sinus somewhat deep, rounded, reaching from the beak 

 to the front, where it terminates in a short rounded extension ; 

 beak prominent, projecting beyond the opposite, arched but not 

 incurved ; area high, arcuate, extending obliquely beyond the 

 beak of the dorsal valve. Surface retaining traces of very fine 

 radiating strice, which are crossed by stronger concentric lines 

 of growth. 



This species is abundant at Louisville and other western localities. It 

 [Senate No. 109.] 9 



