184 REPTiLIA. 



by the pteiygoids which extend forwards to the vomers, and 

 (iii.) by teeth fused with the supporting bone. The ribs are 

 single-headed, except sometimes in the cervical region, and the 

 phalangeal formula of the digits usually resembles that of the 

 lizards, namely 2, 3, 4, 5, 3 [4]. The only definite evidences of 

 evolution consist (i.) in the reduction of the numerous small 

 abdominal ribs to three comparatively large longitudinal series, 

 (ii.) in the superior ossification of the pubis and ischium, and 

 (iii.) in the modification of the fifth metatarsal bone. It is 

 noteworthy that this evolution happened before the period of 

 the Upper Trias. 



Sub- Order 1. Proterosauria. 



The Permian Rhynchocephalia seem to connect the later 

 and more typical members of the order with the Microsaurian 

 Stegocephalia (p. 130) in several respects. The Lower Permian 

 Palceohatteria, for example, has the pectoral and pelvic arches 

 strikingly similar to those of the Microsauria, while its abdomi- 

 nal ribs are merely the ventral armour of the latter slightly 

 modified. Its skull, however, is typically Rhynchocephalian, 

 and the genus must doubtless be placed with the somewhat 

 later Permian reptile, Proteros aunts, in the primitive sub-order, 

 PROTEROSAURIA. As already indicated, this is characterized by 

 the numerous longitudinal series of abdominal ribs, the imper- 

 fectly-ossified aspect of the pubis and ischium, and the non- 

 modified character of the fifth metatarsal bone. 



Palseohatteria (fig. 114). A long-tailed, lizard-like reptile, of small 

 size. The skull exhibits a very short rostral region, enormous orbits, 

 narrow frontals, and slender temporal arcades. There is a pineal fora- 

 men, and the external nares form a pair of small openings at the end of 

 the snout. All the external bones are smooth, and there is a ring of 

 sclerotic plates surrounding the eye. The premaxillae are very small, the 

 maxillae large ; and large conical teeth in a single series are fused with 

 the margin of the jaw. Smaller teeth occur on the vomers and pala- 

 tines. The vertebral centra are delicate constricted cylinders, and small 

 wedge-shaped intercentra (hypocentra) occur between all those in advance 

 of about the sixth caudal. The neural arches are united with the centra 

 only by suture ; zygapophyses are conspicuous, but there are no transverse 

 processes. Ribs with an expanded articular end are borne by all the 

 vertebree as far as the seventh caudal. The approximate number of 



