Anomodontia. Procolophonia and Dicynodontia. 55 



join, but diverge anteriorly ; the palatine bones are small 

 and placed internally to the pterygoids, as in Mammals. The 

 dentition is thecodont (teeth placed in distinct sockets), but 

 the teeth may be anchylosed to the bone. The vertebrae are 

 amphicoelous (concave at both ends), and in some cases the noto- 

 chord pierces them ; the dorsal vertebrae have long transverse 

 processes, and the anterior ribs articulate by double heads. 

 Abdominal ribs seem generally to have been absent. In the 

 pectoral girdle an inter clavicle, clavicles, and precoracoids are 

 present, and a sternum was probably always developed. 



In the pelvis the pubis is placed in advance of the ischium to 

 which it is completely united. The body of the ilium is in advance 

 of the acetabulum. The tarsus has one centrale, and the phalangeal 

 bones of the maims and pes are typically 2, 3, 3, 3, 3, in number 

 as in Mammals ; the whole structure of the foot being Mammalian 

 in type. We are led to conclude, from recent researches, that 

 these animals are directly descended from the Labyrinthodont 

 Amphibians, more especially from the Archegosaurian family. 

 They are also related in all probability to Monotreme Mammals. 



This order appears to be confined to the Permian and Trias. 



SUB-ORDER 1. Procolophonia. 



To the Anomodontia are now referred the small reptiles of 

 the genus Procolophon, with a short triangular and somewhat 

 depressed skull ; their dentition is carnivorous but the marginal 

 teeth are all alike and are completely anchylosed to the bone ; 

 teeth are also borne upon the vomer and the pterygoids. 

 Procolophon presents many points of resemblance to Sphenodon 

 and the Bhynchosauridce. The genus is met with in the Karoo 

 Beds (Trias), of South Africa. 



Table-case, 

 * 



Table-case, 

 No * 18 * 



SUB-ORDER 2. Dicynodontia (Double Dog- toothed). 



Family DICTNODONTID^:. The Dicynodonts* are a very Dicynodon. 

 peculiar family of reptiles from the Trias of South Africa. Wall-case, 

 The skull is massive and remarkable in form, and is furnished 

 with a single pair of huge sharp-pointed tusks growing down- 

 wards, one from each side of the upper jaw, like the tusks in 

 the Walrus. No other kind of teeth was developed in these 

 singular animals ; but the premaxillaries was confluent and 

 sharp-edged, and formed with the lower jaw a beak-like 

 mouth, probably sheathed in horn like that of the Turtles and 

 Tortoises. Several species have been described from the Storm- 



* The genus, Dicynodon, is so called from dia, two, and KVVO$OQ, canine 

 tooth, from the two tusk-like canines in the upper jaw. 



