Diplospondylidce and Archegosauridce. 69 



drerpetum, from the Coal Measures, Nova Scotia; Brachyops, Table-cases 

 from the Permian, Mangali, India; Bothriceps and MiorophoUs, ** s - 22 and 



from South Africa. 



FIG. 91. Bothriceps Huxley I (Lydekberi. Frontal aspect of the skull ; from the 

 Karoo system of the Orange Free State, South Africa. A. 



In Bothriceps the surface of the cranium is closely and 

 irregularly pitted ; the orbits are placed near the middle of the 

 skull. This small skull measures about 2J inches in length, and 

 2 in breadth. It was obtained from the Karoo beds (Triassic?) 

 of South Africa. 



In the Diplospondylidce the vertebras, at least in the caudal 

 region, consist of an anterior centrum carrying the neural arch, 

 and a posterior intercentrum to which the chevrons are united. 

 These interceiitra correspond with those of Glepsydrops among 

 the Anomodontia, the type of structure being known as ein- 

 bolomei'ous. 



In the Archegosauridce each vertebra of the trunk, in Tri- 

 merorachis and Archegosaurus, consists of four portions,* namely, 

 a basal intercentrum (hypocentrum), a pair of pleurocentra, See Table- 

 and a neural arch. This is known as the rhachitomous type of case > No 2 

 vertebra. These are Labyrinthodonts of moderate size, having 

 cylindrical teeth of varying size with only slight infoldings of 

 the dentine ; the upper surface of the skull being pitted ; the 

 supra-occipitals ridged ; a ring of bones is usually developed in 

 the sclerotic ; the ventral surface of the body is always covered 

 with scutes. This family is evidently the most primitive one 

 of the entire group. 



* See Fig. 94, infra, p. 71, vertebra of Eiichirosaurus, illustrating this 

 rhachitomous type of vertebra. 



