558 



ANATOMY OF VERTEBRATES. 



hyo- and hypo-sternal plates on each side being naturally united 

 together ; in Emyda ceylonensis dermal bones are developed from 

 the epi-, hypo- and xiphi-sternals, and from the entosternal or 

 sternum proper, forming seven pieces : the skin of the hinder 

 margin of the broad depressed trunk is strengthened in Emyda 



Inner surface, Carapace, young Tortoise. 



Outer surface, Carapace, young Tortoise. 



by a few dermal ossicles ; much of the skin of the trunk, where 

 not ossified, in Triony tides, has the dermal tissue of cartilaginous 

 hardness. 



In the Turtles, or marine Chelonia, besides the eight connate 

 neural plates, fig. 52, si-ss (p. 61), dermal bones are developed 

 in advance of and behind them, and are commonly unattached 

 to the subjacent vertebra?. The anterior one, ib. ch, is the 

 ' nuchal ' plate : the posterior one, ib. py, is the « pygal ' plate ; 

 the costal plates, ph-ph, articulate suturally with the neural 

 plates, but do not extend to the end of the ribs ; the marginal 

 plates, mi-mi2, are articulated with each other and with the 

 nuchal and pygal plates suturally, and eight on each side receive 

 the ends of the eight ribs supporting the costal plates. Two 



