84 



ARTICULATA. 



No. 149. [894, Cast]. Calymene Blumenbachii, Brongniart. 



This well known genu.s derives its name from the 

 obscurity which long hung over the real nature of 

 these crustaceans. In this species, the cephalic 

 shield is large, convex, rounded in front, with a 

 well marked border, boldly three-lobed, and having 

 prominent, but not very large ej^es, set widely apart ; 

 the thoracic portion consists of thirteen segments; 

 and the pygidium is small and nearly semi-circular. 

 It is often foimd coiled up. This specimen is from 

 the Upper Silurian at Dudley, England. The origi- 

 nal is in the Ward Collection in the University of 

 Rochester. 



No. 150. [398, Cast]. Ceraurus pleurexanthemus, Green. 



This genus is closely allied to the Ackl- 

 aspis of Murchison. In this species the 

 buckler is crescent form; the eyes small, 

 distinct and granulated ; the glabella deeply 

 furrowed on each side; the thorax has 

 eleven articulations, and the caudal shield 

 four. This specimen is a restoration by 

 adjustment of fragments from different 

 individuals discovered in the Trenton 

 Limestone and Hudson River Group 

 (Lower Silurian). 



No. 151. [407, Cast]. Dalmania (Phacops) limulurus, Green. 



This Trilobite, also called Asaphus limulurus, is one of the 

 most common forms. It has a sublunate buckler, a lobed 

 glabella, eyes of medium size, eleven body articulations, and 

 tifteen caudal. The body and caudal portion is more fre- 

 quently found separated from the cephalic shield. This 

 specimen is from the Niagara Group (Upper Silurian) at Lock- 

 port, N. Y. 



No. 152. [409, Cast]. Dalmania myrmecophora. 



Pygidium. This specimen shows the broad, moderately convex caudal 

 shield, with thirteen rings beautifully ornamented with a double row of nodes. 



