No. 3.] PELVIS OF THE TESTUDINATA. 351 



In Wagler's figures the cartilages are not indicated. It is im- 

 portant to re-examine young and fresh specimens. The pubo- 

 ischiadic foramina are very small; the mesogastroid seems to 

 be greatly developed. The entopubes have a strong posterior 

 branch, as in the Emydidae and Chelydridse, and also some of 

 the fossil Cheloniidas, and meet in the middle line. The ischia 

 are of the type of the Pinnata, and so is the ilium. Hoffmann 

 figures a very strong epigastroid. It seems that Dermochelys 

 developed from one of the more generalized Pinnata, which 

 still possessed the posterior branch of the entopubis of the 

 Chelydridae. 



Fig. 9. — Trionyx. 



E, Epigastroid. 



M, Mesogastroid ligament. 



In the Trionychidae we have a stage still more advanced than 

 that seen in the Cheloniidae. The mesogastroid is only repre- 

 sented by ligament, and entopubes and entoischia are far 

 separated ; there is a well-developed cartilaginous epigastroid ; 

 the hypogastroid is exceedingly small. This condition must 

 already have existed in the forms of the Laramie Cretaceous, 

 in which the pelvis is not different from the living forms. That 

 the Trionychian ancestors had a pelvis with a cartilaginous 

 mesogastroid, and a pubis with a posterior entopubic process, 

 there cannot be any doubt. I also believe that the young or 

 embryonic Trionychidas will show the mesogastroid ligament 

 represented by cartilage. 



Pleurodira, 



It was the peculiar condition seen in the pelvis of the 

 Chelyiidae, which induced me to examine the pelvis of the Tes- 



