RHYXCJKK KPHALIA. 333 



They make their appearance in the Permian and they are therefore 

 the oldest known reptiles. For this reason and also on account of the 

 above-mentioned resemblances to other reptilian groups they have been 

 regarded by some authors as an ancestral group or at least as being closely 

 allied to the ancestors of reptiles generally and possibly of birds. We do 

 not share this view. The Rhynchocephalia are essentially reptilian, i.e. 

 they present so far as we know them all the typical features of reptilian 

 organisation in full development. This is hardly what we should expect 

 if they were an ancestral group. It is true that the earlier forms from the 

 Permian are very imperfectly known, but this fact can hardly be alleged 

 as an argument in favour of the view that they are ancestral. Doubtless 

 the view would not have been put forward had it not been for the earliness 

 of their appearance as fossils. But arguments based on this fact lose 

 much of their weight when w r e consider the necessary imperfection of the 

 geological record. The fact that fossil remains of any particular animal 

 are not found in any particular strata cannot be regarded as evidence of 

 the non-existence of the animal. If it could we should have to regard the 

 living genus Splienodon as being totally disconnected with the other eenera 

 of its family, for the family Sphe-nodoniidae is not found fossil after the 

 Jurassic period. Again the Chelonia make their appearance in the Triassic 

 strata with all the specialities of the order. When we consider the small 

 change which has taken place in the organisation of the Chelonia or indeed 

 of the Crocodilia since the Triassic age, is it reasonable to suppose that they 

 were evolved from sphenodon-like forms in the interval comparatively 

 short which elapsed between the laying down of the Permian and Triassic 

 strata ? The Chelonia of the Trias must have had predecessors. It can 

 hardly be regarded as an unreasonable view to hold that their remains per- 

 haps in a less specialised form will some day be found in the Permian or 

 perhaps even earlier ; and even if they are never found in those earlier 

 strata, it is hardly open to us to argue that they did not exist before the 

 Triassic age, unless indeed we give up the evolution hypothesis altogether and 

 assume that they came into existence suddenly and without predecessors. 

 And if they existed before the Triassic age the argument that the 

 Rhynchocephalia are ancestral to them, in so far as it is based on their 

 antiquity, is much weakened, if it does not completely fall to the ground. 

 As already stated the Rhynchocephalia are represented at the present 

 time by the genus Sphenodon which lives in New Zealand, and so far as we 

 know has not been found in the fossil state. 

 The group may be classified as follows : 



Protorosauridae. Premaxillae, maxillae and mandibles with conical 

 teeth either implanted in shallow pits or fused with the jaws. Vomer 

 covered with small teeth. Interclavicle rhombic in front, prolonged 

 behind. Permian and Trias. Palaeohatteria Credner, long-tailed small 

 lizards 45 cm. in length, vertebrae amphicoelous with continuous notochord, 

 abdominal ribs as numerous small oat-shaped scutes, Lower Permian, near 

 Dresden. Protorosaurus H. v. Meyer, the Thuringian lizard, to (j or 7 

 feet ; with long neck ; skull and limb girdles imperfectly known, intercentra 

 in the neck only, vertebrae amphicoelous, neurocentral suture obliterated, 

 limbs well developed, Upper Permian of Thuringia ; Telerpeton Man tell, 

 Elgin Sandstone (Trias). 



Fragments from the Permian of Texas and the Lower Permian of 

 Bohemia known as Clepsydrops, Dimeirodon, Naosaurus, etc. seem to be 

 allied here. They have been classed as Pelycosauria and many of the 

 genera have enormous neural spines with lateral branches. 



