(is). Make a drawing of the dorsum of the skull, showing 



orbits and temporal fossae. 

 (i6). Compare the sktill with that of No. 15. Result? 

 (20). The body of ttirtles in encased in a bony box, the dorsal 

 portion of which is called the carapace, and the ven- 

 tral portion the plastron. Both carapace and plas- 

 tron are covered with thin, homy scutes or shields. 

 Before identifying the specimen, study the scuteUa- 

 tion and make a drawing of both carapace and 

 plastron. 



(a) . Carapace — The row of scutes forming the mar- 

 gin of the carapace are the marginals. The 

 narrow marginal scute situated on the middle 

 line above the neck is the nuchal. The two 

 marginals above the base of the tail are the 

 supracaudals. The scutes extending along 

 the middle line of the back are known as the 

 vertebrals. The costals are those scutes be- 

 tween the marginals and the vertebrals. 

 (b). Plastron — In the plastron are six pairs of 

 scutes. The most cephalic pair, placed 

 directly beneath the neck, are the gulars. 

 The others named in order from the gulars 

 caudad are : humerals, pectorals, abdominals, 

 femorals, anals. Caudad of the arm, be- 

 tween the carapace and the plastron, is the 

 axillary scute, and in a similar position 

 cephalad of the leg is the inguinal. In some 

 species both axillary and inguinal scutes are 

 more numerous. 

 (21). Drawings of the ventral and the lateral aspects. 

 (23). Drawings of the dorsal and ventral aspects. 

 (24.) Drawings of the ventral aspect. 

 (26). Drawings of the ventral and the lateral aspects. 

 (28). A jarof miscellaneous specimens to be identified if time 

 permits. 



20 



