202 



CEP HAL A SPIDOMORPHI 



In the Ateleaspidae the scales on the sides of the body are set 

 in transverse rows, which fuse at the sides to transverse plates in 



Cephalaspis Lyelli, Ag. ; restoration of dorsal shield. (After Lankester, from A. S. Wood- 

 ward.) a./, antorbital fossa ; a.p, antorbital prominences ; i.g, interorbital groove ; i.p, inter- 

 orbital plate; m.c, 'marginal cells'; o.r, orbital rim; p.a, posterior angle; p.c, posterior 

 cornu ; p.ov, postorbital depression ; p.r, posterior ridge ; p.s, posterior spine ; r, rim. 



ma. 



-\-~pa. 



FIG. 176. 



Tremataspis Schmidti, Rohon, enlarged. A, ventral, and B, dorsal view of the shields. 

 (After Patten.) a.a, anterior area with polygonal plates ; a.m.o, anterior median opening ; d.s, 

 dorsal shield ; l.l, pits of lateral line ; m, mouth ; m.a, median area with plates ; or, orbit ; p.a, 

 posterior area with plates ; pl.o, lateral opening ; v.o, ventral openings, probably branchial ; 

 v.p, ventral plates ; v.s, ventral shield. 



