TERRESTRIAL VERTEBRATA. 



24^ 



arch, from resting by more than luilf its base on the intereentrnm (Fig. 3) gratliiuUy 

 transfers itself to the centrum, at the base of the caudal series. It maintains this 

 position throughout the lumbar and dorsal series,* resting freely in an angular fossa 

 of each side of the anterior three-fourths of the superior lace of the centrum. It bears 

 the diapophysis with the usual articulation for a single-headed rib (Plate I, Fig. 3). 

 Tlu' intercentra even continue to the cervical region, wliicli terminates anteriorly in an 

 intercentrum, which is perhaps the body of the proatlas, the processus dentatus of the 

 atlas of the existing Batrachia, and the occipital condyle (without basioccipital bone) 

 of the Tieptilia. t Iu addition to the preceding reasons for adoi)ting my determination 

 of centrum and intercentrum, it may be added, that in the Cricoius lieteroclllus Cope 

 the dorsal intercentra are much narrowed above,J some of them so much so as to have 

 a sharp edge, which forms but a narrow bi'idge above the foramen (Plate T, Figs. 7-8) 

 chordte dorsal is. 



According to Gaudry, the structure of the dorsal part of the vertebral column in 

 Aetinodon and Arehegosaurus is identical with that of Eryops§ (Fig. 4). This 



;/<;;) 



Fio. 4. — ArchegoMurus decheni GoMil. Section of dorsal vertebra', restored by Giiudry ; natural size. Let. n, </, 

 neural arch ; c, neural canal. 



Fio. 5. — Tlie same species ; dorsal verlebne, copied from Fritscli ; nalunil size. Letter t", Interrenlrum ; p, cen- 

 trum ; pz, poslzygaiiO]>liysis ; n. >p., neural spine. 



author represents the neural arch as resting on the pleuiocentruni. Fritscli, on the 

 other hand, II represents the neural arches as slightly in contact with the intercentra, and 



• Proceedings Amcr. Pliilosopli. Soc, 1884, p. 29. 



t Anier. Naturalist, 1884, p. 37. 



X Proceeds. .\mer. Pliilos. Society, 1877, p. 186 (see C. diicophorus, wliicli was founded on such intercentra) 



§ Enchalnements du Monde Animal, Fossiles Primaircs, p. 2G1, fig. 259. 



I Fauna dcr Goskohle, Tab. 58, fr. 13. 



