TRILOBITA—PROPARIA. 



323 



of thoracic axis bearing a spine. Pleural segments of pygidium 

 strongly grooved medially, giving them a dichotomous appearance ; 

 this medial depression does not show upon the internal mold. 

 Glabella and genal angles pustulose; remainder of test smooth. 

 Oriskany of Ontario; Onondaga of New York. 



Fig. 1637. Phacops cristata. (After 

 Hall. ) 



Fig 1638. Phacops rana. (After 

 Hall.) 



173. P. rana (Green). (Fig. 1638.) Devonic. 



The two anterior glabellar furrows obsolete. Eyes with 40 to 

 50 lenses arranged in eight to ten diagonal rows. Entire test 

 strongly pustulose. 



Hamilton and Onondaga throughout eastern North America. 



LXVIII. Pterygometopus Schmidt. 



Very similar to Phacops but the cephalon is obtusely angular in 

 front and the lateral furrows of the glabella are well defined. 

 Ordovicic. 



