Diplospondylidce and Archegosauridce. 



69 



drerpetum, from the Coal Measures, j!^ova Scotia; Brachyops, Table-cases 

 from the Permian, Mangali, India; Bothriceps and Micropholis, Nos. 22 and 

 from South Africa. 



Fig. 91.—BotkHccps Huxku'i (Lydekker;. Frontal aspect of the skull ; from the 

 Karoo system of the Orange JFree State, South Africa. *. 



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 2^ inches in length, and 

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

 of South Africa. 



In the Biplospnudylidce the vertebra3, at least in the caudal 

 i^egion, consist of an anterior ceiitrum cai-rying the neiiral arch, 

 and a posterior intercentrum to which the chevrons are united. 

 These intei'centra correspond with those of Clepsydroys among 

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

 holo'inerous. 



In the Archegosauridce each vertebra of the tru.nk, in Tri- 

 tnerorachis and Archegosannis, consists of four portions,* namely, 

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

 and a neural arch. This is known as the rhachltomous type of ^^^e, No. 23. 

 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, Tcvtcbra of Eiichtrosaurus, illustrating this 

 rhachitomous tjpe of yertebra. 



