EXPLANATION OF PLATE XLV. 



Cbioceras nautiloides, Eth.fd. 



Fig. 1. Lateral view of a natural cast with overhanging whorls, and very 

 convex Hanks. On the inner half whorl the costae are fasciculate 

 in bundles of two or three, and the uniting tubercles large and 

 blunt ; the remainder of the costas are devoid of tubercles. Slightly 

 less than half natural size. 

 ,, 2. Ventro-dorsal view of Fig. 1, displaying the broad rounded venter, 

 nontuberculate costse, overhanging whorls, and the very broad- 

 oval section. Slightly less than half natural size. 



