THE PTERASPIDA. 



B 



fn.m. 



C 



FIG. 244. A, Restored outline of the cephalic shield and cephalic appendages of Cyathaspis, seen from the 

 neural surface, based largely on Lindstrom's specimen from the Silurian rocks of Gothland; B and C, partly restored 

 outlines of two individuals of Palseaspis (male and female?)from Perry Co., Pa. The shell has been removed, showing 

 a cast of the inner neural surface. About natural sice. 



-do. 



FIG. 245. Cephalic buckler of Pteraspis, neural surface. (After Lankester, slightly modified) About natural size 



