1062 



CLASS REPTILIA. 



from the Permian of North America, and includes Diadectes, Em- 

 pedias (Empedocles), and Helodectes. The teeth (fig. 984) are 

 transversely elongated like those of Bolosaurus, and are also 

 divided by a median vertical ridge ; but both the inner and the 

 outer moieties are equally low. Their alveoli are not separated, 

 and the edges of the crowns are obtuse, with tuberosities on some 

 of them distinct from the apex of the main ridge. Professor Cope 

 regards this peculiar type of dentition as indicative of a herbivorous 

 diet. The brain-case differs from that of the Clepsydropidce in a 

 manner analogous to that in which the brain-case of the Varanidce 



Fig. 983. — Lateral view of 

 a premaxillary tooth of Deu- 

 terosattrus biarmicus ; from 

 the Upper Permian of Russia. 

 Half natural size. 



Fig. 984. — Lateral and palatal view 

 of a posterior tooth of Empedias mo- 

 laris ; from the Permian of North 

 America. 



is distinguished from the same part in other Lacertilia — that is, it is 

 continued between the orbits so as to enclose the olfactory lobes 

 in bone. Phanerosaurus, from the Permian of Germany, is referred 

 by Professor Cope, from the structure of its vertebrae, to this or the 

 preceding family. 



Suborder 3. Dicynodontia. — In this suborder the vertebrae 

 have no notochordal canal ; intercentra are wanting ; and the 

 sacrum includes from four to five vertebrae. There is in no case 

 more than one pair of teeth in the alveolar borders of the 

 upper jaw, while there are none in those of the mandible. The 

 palate is of the general type of that of the Theriodonts, but the 

 premaxillae unite to form a single beak-like bone, and the mandibular 

 symphysis, which is very deep and laterally compressed, is likewise 

 anchylosed. The nares are double ; and it is probable that in some 

 forms a part or the whole of the alveolar borders of the mandible 

 was sheathed in horn ; while the mandibular rami have lateral 

 vacuities (fig. 985, b). There is a single temporal arcade, which 

 appears to be a squamoso-maxillary one. In the pelvis the ilium is 

 much expanded in an antero-posterior direction, the expanded plate 



