RAJ1FORMES 



153 



remains, of simpler structure than the modern species, are found in the 

 Cretaceous of Mount Lebanon (A. S. Woodward [503]). 



Pristiophorus, M. and H. ; Pacific ; Cretaceous, Mt. Lebanon. Plio- 

 trema, Kegan, S. African. 



FIG. 115. 

 Fristiophorus firrdtus, Lath., 9. (After Jaekel, from Dean.) 



Sub-Order 2. RAJIFORMES. 



The body becomes more or less depressed. The branchial slits 

 take up a distinctly ventral position ; while the large crescentic 

 spiracle, which is now inhalent, remains near the eye, on the dorsal 

 surface. A movable valve, containing the prespiracular cartilage, 



FIG. lie. 



A, Zygaena tudes, Cuv. (After Cuvier.) B, dorsal view, and C, ventral view of Rhina 

 s<fuatin<i. ad, first dorsal fln ; c./, caudal fin ; g, gill-slit ; n, nostril ; p.f, pectoral fin ; j>c, 

 pelvic tin ; r, rostrum with lateral teeth ; sp, spiracle. 



is formed on its anterior face (Division 2). The movable eyelids 

 are lost. The tail becomes reduced in size, less heterocercal ; and 

 the dorsal fins shift backwards, even the first being always behind 

 the pelvic, on the tail. The trunk appears to spread outwards, 

 chiefly owing to the enormous development of the pectoral fins. 

 These not only may extend backwards so as to meet the pelvic 



