CRUSTACEA. 

 No. 144. [373, Cast]. Asaphas gigas, Dalmann. 



This huge Trilobite, the Isotelus 

 gigas of DeKay and Isotelus meffistos 

 of Locke, has an oval form and con- 

 vex surface; the head and tail nearly 

 equal, and both subtriangular; well 

 developed eyes; eight body seg- 

 ments; and no glabella, nor any ribs 

 on the tail. This cast is a restoration 

 bj^ Professor Locke from fragments 

 discovered in the Trenton limestone 

 (Lower Silurian), in Adams County, 

 Ohio. It is well adapted for lecture 

 purposes, exhibiting on a large scale 

 the prominent parts of these ancient 

 Crustaceans. 



Size, 22 X 14. 



83 



No. 145. [386, Cast]. Acidaspis Buchii, Barrande. 



This Trilobite is distinguished generically by its small 

 but strongly arched body-rings, and by the surface being 

 covered regularly with tubercules. This specimen is from 

 the Lower Silurian slate at Beraun, Bohemia. 



No. 146. [390, Cast]. Biimastus (Illaenus) Barriensis, Murch. 



This genus of Trilobites is characterized by the great 

 breadth and convexity of the cephalic and caudal plates, and 

 the faintness of the longitudinal, trilobite markings. The 

 genus closely resembles lUcenus, and this species is only dis- 

 tinguisli^d from lllmnus crassicauda by the fact that the broad 

 axis is not strictly separated from the lateral lobes. The 

 specimen is from the Niagara Group (Upper Silurian), New 

 York. 



No. 147. Calymene niagarensis, Hall. 



Two Specimens. From the Niagara Group at Grafton, 111. 



No. 148. Calymene senaria, Conrad. 



Two Specimens. From the Cincinnati Group, Waynesville, Ohio. 



