1 132 CLASS REPTILIA. 



palatines ; 1 and the premaxillse never united. The dentition is 

 usually acrodont. The ribs may have uncinate processes, and ab- 

 dominal ribs are always developed. The vertebrae may be either 

 opisthoccelous or amphiccelous, and intercentra may be retained. 



Dr Baur observes that " the Rhynchocephalia, together with the 

 Proterosauria, to which they are closely allied, are certainly the 

 most generalised group of all Reptiles, and come nearest, in many 

 respects, to that order of Reptiles from which all others took their 

 origin." 



This order, if we include Palceohatteria, dates from the Permian, 

 but only comparatively few forms are at present known. It may 

 be provisionally divided into three suborders. 



Family Pal^ohatteriid^. — The genus Palceohatteria, of the 

 Permian of Germany, is regarded by Professor Credner, its describer, 

 as so closely allied to the existing Sphenodon that it is referred by 

 him to the same family. There can, however, be no question but 

 that it is entitled to be the representative of a distinct family, and 

 probably of a distinct suborder. Dr Baur, with whom Professor 

 Cope is in accord, would even go farther, and remove this genus 

 altogether from the Rhynchocephalia, to place it with Mesosaurus 

 in his order Proganosauria. There is, indeed, much to be said in 

 favour of placing both these primitive Reptiles in a single group ; 

 but this appears to be outweighed by the resemblance of the one to 

 the true Sauropterygians and of the other to the Rhynchocephalians. 



The skull much resembles that of Sphenodon, the jugal dividing 

 posteriorly to join the two temporal arcades ; but the supra- and 

 infratemporal fossae are much smaller, while there is a separate 

 lachrymal, and the premaxillse do not form a beak. Teeth occur 

 not only on the palatines, but also on the vomer and pterygoids, as 

 in the young of Sphenodon ; and Dr Baur suggests that there was 

 a parasphenoid. There are intercentra between all the vertebrae, 

 in which the neural arches remain distinct from the centra ; there 

 are also two sacral vertebrae ; and the ribs have no uncinate pro- 

 cesses. The teeth of the jaws were acrodont, and anchylosed to 

 the bone. The pectoral girdle presents an approximation, in the 

 form of the clavicles and interclavicle, to that of Sphe?iodon ; but 

 the expanded proximal extremities of the clavicles recall the lateral 

 thoracic plates of the Labyrinthodonts, and the coracoid is more 

 like that of the Sauropterygians. This bone, indeed, like the bones 

 of the pelvic girdle, ossifies by radiations from the centre after the 

 manner obtaining in Sauropterygians and Amphibians. The pelvic 

 girdle is widely different from that of Sphenodon ; the pubes and 

 ischia forming wide flattened plates like those of the Sauropterygian 



1 The same arrangement obtains in the skull of Nothosanrus, represented in 

 fig. 991. 



