THE CARAPACE. II 



utes, giving first another dose of chloroform (2) should 

 there be the least sign of sensibility remaining ; the tor- 

 toise-shell can then be peeled off. When it is removed, 

 note that though the bones beneath present surface- 

 markings corresponding to the edges of the epidermic 

 plates, their actual number and arrangement are quite 

 different- 



9. The Bony and Cartilaginous Skeleton. — For the sat- 

 isfactory study of the skeleton, the student should have 

 beside him a prepared articulated skeleton for reference, 

 and should disarticulate and examine another skeleton 

 for himself. For this purpose boil the animal thor- 

 oughly ; the plastron can usually then be separated from 

 the carapace by seizing each and pulling them forcibly 

 apart ; if this prove impracticable, divide the uniting 

 bridges by a saw, then cut through the soft parts at- 

 tached to the dorsal aspect of the plastron and remove 

 the latter ; clean all the bones carefully, but for the pre- 

 sent do not separate from one another the pieces of 

 the plastron, carapace, skull, manus, and pes. In the 

 cleaning take great care not to injure the cartilaginous 

 portions of the skeleton. 



10. The Carapace is composed partly of dermic exo- 

 skeletal bony plates, and partly of true endoskeletal 

 elements. The dermic bones are printed below in small 

 capitals. 



a. On the exterior of the carapace, note a median 

 row of bones succeeding one another, from be- 

 fore back, in the following order : the Nuchal 

 Plate, rhomboidal in shape ; eight neural plates, 

 formed by the expanded spines of the dorsal 



