2 6 REPTILES 



Of the various groups of reptiles, the entire subclass 

 Theromorpha appears to have been confined to the Permian 

 and Triassic periods ; its oldest known representatives being 

 probably those from the Permian of Texas. Whether the 

 latter strata are somewhat older or newer than (it is unlikely 

 that they are the exact equivalent in age) the Lower Permian 

 of Europe, cannot be determined ; and it is therefore impos- 

 sible to say whether the Theromorpha are older than Ornitho- 

 morpha, or vice versa. Be this as it may, the Theromorpha, 

 as represented by the Pariasauria, probably originated from 

 the labyrinthodont stegocephalians in the Permian, or, at all 

 events, in the later Carboniferous ; while the Theriodontia 

 probably gave rise to mammals in the Trias. Having achieved 

 this triumph, their task appears to have been accomplished, and 

 they gradually waned and finally disappeared from the scene. 

 Previous to, or about, the time that they gave rise to the 

 Mammalia, the Theromorpha appear to have been the dominant 

 forms of terrestrial vertebrate life, the contemporary rhyncho- 

 cephalians, like most of their successors, being comparatively 

 small creatures. For a long period their descendants the 

 mammals were, however, at least over a large part of the 

 world, in a subsidiary position ; and did not in fact regain the in- 

 heritance of those reptilian ancestors as the lords of creation 

 till the Tertiary period. 



Turning to the second, or bird-like brigade (Ornithomorpha), 

 we find that the most primitive order, namely the Rhyncho- 

 cephalia, is the most ancient, or, at all events, as ancient as the 

 nearly related Pelycosauria (on the supposition that it is the 

 ancestor of all the class, it must of course be the oldest). As 

 already said, its oldest known representatives are PaUeoJiatteria 

 of the Lower Permian and Protorosaurns from a somewhat 

 higher stage of the system ; the presumed evolution from the 

 microsaurian stegocephelians having probably taken place in 

 either the Lower Permian or the Upper Carboniferous. In the 

 Trias the rhynchocephalians were well represented, and they are 

 known by several forms from the Jurassic, while there is evi- 

 dence of their existence in the Cretaceous. The links between 

 the Jurassic forms and the existing New Zealand species are, 

 however, still unknown, and may not improbably have 

 flourished in southern lands which have long since been sub- 



