136 



BATRACHIA. 



It occurs in the Lower Permian of Rhenish Prussia, but the 

 finest specimens have been obtained from Autun, France. 

 Euchirosaurus, from Autun, is more imperfectly known, ex- 

 hibiting truly rhachitomous vertebrae with the neural spines 

 expanded at the upper end (fig. 88). Dissorophus, from the 

 Permian of Texas, has the neural spines still more expanded at 

 the upper end, these supporting a carapace of transversely- 

 elongated bony dermal scutes. Eryops, from the Permian of 

 Texas, also seems to be related, but bears minute denticles on 

 the inner side of the mandibular ramus. 



(,.0. 



Euchirosaurus rochei ; posterior (A) and lateral (B) aspects of rhachitomous 

 vertebra, about nat. size. L. Permian ; France, al., lateral expansion of 

 neural arch ; c, facette for rib ; c.r., neural canal ; d, transverse process of 

 neural arch ; i.e., hypocentrum ; n, neural spine ; not., space originally 

 occupied by notochord ; pl.c., pleurocentra ; s, suture between neural arch 

 and spine ; z.a., z.p., anterior and posterior zygapophyses. ( After Gaudry.) 



Cricotus. This imperfectly-known genus is chiefly interesting on 

 account of the condition of the vertebral column. In the presacral region 

 the pleurocentra and hypocentra are horse-shoe-shaped, the former alone 

 bearing the neural arches, which have each a pair of transverse processes. 



