CHELONIA. 



Efe. l. 



Carapace of the Loggerhead Turtle [Cheloue eaouannd). 



and of a lateral series of " costal scutes " there 

 is also a peripheral series of "marginal scutes'" 

 corresponding with and impressing the mar- 

 ginal plates. The nuchal plate (c/i) is 

 remarkable for its breadth in all Chelonia, 

 and usually sends down a ridge from the 

 middle line of its under surface, which is 

 attached by ligament to the summit of the 

 neural arch of the first dorsal vertebra. The 

 first true neural plate, si, is much narrower, 

 and is connate with the summit of the neural 

 spine of the second dorsal vertebra ; the 

 succeeding vertebral neural plates, s2—ss, 

 have the same relations with the succeeding 

 neural spines, but the ninth, tenth, and 

 eleventh, like the nuchal {ch) and pygal 

 (pi/), plates are independent ossifications in 

 the substance of the derm. The costal 

 pieces of the carapace are supra-additions to 



eight pahs of pleurapophyses or vertebral ribs, those, viz. of the second to the ninth 

 dorsal vertebras inclusive. The slender or normal portions of the ribs project freely 

 for some distance beyond the expanded 

 and connate portions (" costal plates" of 

 the carapace), along the under surface 

 of which the rib may be traced, of its 

 ordinary breadth, to the neck and head, 

 which liberates itself from the costal 

 plate to articulate to the interspace of 

 the two contiguous vertebral bodies, 

 (centrums), to the posterior of which 

 such rib properly belongs. 



The woodcut (fig. 2) illustrates this 

 structure : ch shows the inner side of 

 the nuchal plate ; c\ is the first rib, 

 articulated to the fore part of the body 

 of the first dorsal vertebras ; pl\ is the 

 first rib of the carapace (the second rib 

 of the dorsal series), connate with the 

 first costal plate ; ph to pis, are the 

 succeeding ribs and costal plates of the carapace. 



Inner view of carapace of the Loggerhead Turtle. 

 {Chelone cctouanna). 



The heads of the ribs articulate to 



