90 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



This species is well characterized by the convexity of the pygidium, and 

 angular axis with the crest of short spines. 



Geological formation and locality. In limestone of the Upper Helder- 

 berg group : Falls of Ohio, in Stratum Y of Mr. Lyon's section*. From 

 S. S. Lyon, of Jefifersonville. 



DALMANIA PLEIONE ( n. s.). 

 Pygidium convex : axis prominent. Lateral lobes flattened near the 

 axis, and abruptly bent downwards at the sides. Axis marked by 

 about nine or ten rings; the lateral lobes marked by five or six 

 ribs, five of which on each side are prolonged into sharp rounded 

 spines, and the caudal extremity produced in a short wide tri- 

 angular process, which is not more than half the length of the 

 lateral spines. 



This species belongs to the group of which the Dalmania {CryphcBus) 

 hoothii may be regarded as the type : it has the pygidium more convex 

 than that species, and the lateral spines are proportionally larger, more 

 rounded and more widely spreading, while the caudal prolongation is a short 

 deltoid process. 



Geological formation and locality. In limestone of the age of the Upper 

 Helderberg group, at the Falls of the Ohio. 



DALMANIA ERINA ( n. s.). 

 Pygidium paraboloid : length and width, at the anterior side, 

 about as three to four; axis very prominent, subangular, slightly 

 compressed along the sides, marked by fourteen or fifteen rings. 

 Lateral lobes nearly flat for more than half their width, bending 

 abruptly downwards at the sides. Ribs twelve or thirteen, termi- 

 nating abruptly in a spreading border which is scarcely marked 

 by the furrows beyond the ribs : a faint impressed line along the 

 centre of the ribs from the outer extremity to near the longitudi- 

 nal furrow, where it bends gently downwards to the lower side. 

 Surface finely granulose. 



This species is readily distinguished from either of the preceding, by the 

 prominent axis, wide and plain border, and surface without nodes or spines. 

 The most characteristic specimen lias a width, at the anterior margin of the 

 pygidium, of one inch, and a length of three-fourths of an inch. 



Geological formation and locality. In limestone of the Upper Helder- 

 berg group, at Williamsville, N.Y. 



* Transactions of the Academy of Sciences of St. Louis, Vol. i, p. 614. 



[ September, 



