SO' ANATOMY OF A CHELONIAN. 



ing from the occiput to the cervical vertebrae, 

 and beneath which it passes to join its fellow. 

 Into this cross branch opens, on each side, a 

 vein from the exterior of the cranium, and 

 also one from inside the skull cavity. 

 c. Beyond the point where the subclavian vein 

 receives the external jugular, it gets a branch 

 from the regions near the base of the neck on 

 the dorsal aspect; it then continues to the 

 forelimb. 



119. The outer division of the superior cava crosses 

 over the armpit, receiving some branches in that region, 

 and then runs, as the internal mammary, along the mar- 

 gin of the carapace with the artery of that name (96, g). 



120. Before proceeding to study the inferior vena 

 cava, it will be necessary to dissect the Genito-nrinary 

 Apparatus. Endeavor to get your next specimen (193) 

 of the other sex,* and on it complete the examination 

 of the reproductive organs. 



121. If your present specimen be a female, proceed 

 next to section 138 ; if it be a male, examine the 

 Male Reproductive Organs; for this purpose divide the 

 pelvic bones along the median ventral line and push 

 the halves apart ; then divide the muscles beneath. 



*It is not easy to tell the sex of a Slider from external exam- 

 ination ; dealers profess to tell by a supposed greater convexity of the 

 posterior part of the carapace in the female. But we have not found 

 this reliable. When a number of students are v^orking together in a 

 laboratory, they will, however, be able to arrange it between them so that 

 all shall get a specimen of each sex. 



