1030 



CLASS AMPHIBIA. 



scutes ; and the palatines form long splints lying on the inner side 

 of the maxillae. This family is evidently the most primitive one 

 of the entire order ; the vertebral column displaying an arrest of 

 development at a stage which is transitional in higher forms. It is 

 further remarkable for the small size of the coracoid, in which respect 

 this group agrees with the Salamanders and some of the Anomo- 

 dont Reptiles. The humerus has distinct condyles, as in the latter 

 group ; and in the pelvis the pubis is ossified, and, like that of some 

 Anomodonts, unites with the ischium without the intervention of 

 an obturator foramen. The tarsus and carpus (fig. 959) are 



Fig. 960. — Left lateral aspect of the arch and intercentrum, and posterior aspect of the arch, 

 of a dorsal vertebra of Euchirosaurus Rochei', from the Lower Permian of France, n, Neural 

 spine, with lateral expansions, al ; s, Suture between spine and arch ; z.a, Pre-, zp, Postzyga- 

 pophysis ; d, Transverse process ; c, Rib-facet ; c.r, Neural canal; i.c, Intercentrum. (Adapted 

 from Gaudry.) 



characterised by the number of centralia, there being, according 

 to the interpretation here followed, four of these bones in the 

 former and three in the latter ; and the first centrale articulating 

 respectively with the tibia in the tarsus and with the radius in 

 the carpus. This type of tarsal and carpal structure is evidently 

 the most primitive yet observed. 



In Archegosaurus, and also in Zygosaurus of the European Per- 

 mian, and Trimerorhachis of the reputed equivalent strata of North 

 America, the occipital condyles were not ossified ; but they were 



■Hi 



