346 BAUR. [Vol. IV. 



mesogastroid ; the portion behind the entoischia, the hypogas- 

 troid (hypoischium, os cloacae). For the correct understanding 

 of the pelvis of vertebrates it is necessary to introduce these 

 terms. The foramina on each side between pelvis and ischium 

 are called foramina pubo-ischiadica ; the small foramen in the 

 pubis, obturator foramen.^ 



It is very easy to derive all conditions seen in the pelvis of 

 the Testudinata from the condition of Sphenodon just de- 

 scribed. 



We start from the Chelydroids as a general type. In the 

 young Macrochelys and Chelydra we have the gastral cartilage 

 complete and well developed. The epigastroid forms a very 



Fig. 2. — Macrochelys Temminckii 

 (Troost. MSS.). 



E, Epigastroid. 

 M, Mesogastroid. 

 H, Hypogastroid. 

 /, For. pubo-isch. 



a, Entopubis. 



b, Ectopubis. 



c, Entoischium. 



d, Ectoischium. 



massive, long, anterior process ; the hypogastroid is very slen- 

 der, ending in a point behind. In old specimens the entopubes 

 touch each other in the middle line, separating epigastroid and 

 mesogastroid ; the entoischia also meet, separating mesogastroid 

 and hypogastroid. Ossification may take place from different 

 centres in the epigastroid, mesogastroid, and hypogastroid. En- 

 topubes and entoischia never meet, but are always separated by 

 the mesogastroid. 



From the Chelydridae we reach the conditions seen in the 

 Cinosternidas through the Dermatemydidae and Staurotypidse.^ 



1 The obturator foramen may be placed completely in the pubis, or on the border 

 of the pubis, or in the pubo-ischiadic foramen. 



2 I am now able — thanks to Professor Riitimeyer — to give additional characters 

 for the Chelydridae, Dermatemydidfe, Staurotypidse, based on the shoulder girdle, the 

 pelvis, and the conditions of the ninth and tenth dorsal vertebra. 



Chelydrida:. No anterior process on entoscapula near acetabulum ; no posterior 

 process on coracoid near acetabulum; mesogastroid well developed, separating com- 

 pletely entopubes and entoischia; no anterior process on ilium; rib-head of eighth 



