290 Frof. H. G. Seeley. Researches on the Structure, [June 21. 



the ilium is thin, but imperfectly exposed ; and the ischia are shaped 

 as in Pliosaurus, but the pubis does not closely resemble that of any 

 reptile. The femur has the inferior internal trochanteric ridge only 

 slightly developed. There is no neck defining the head of the bone 

 from the shaft. The fibula is slender; no indication of a patella is 

 preserved. Below the stout tibia, the proximal row of the tarsus 

 appears to consist of two bones, an inner astragalus with hemis- 

 pherical proximal surface, and a narrow elongated bone which 

 appears to be the calcaneum. There were three or four bones in the 

 distal row of the tarsus, but only one is preserved. The digits are 

 nearly parallel with each other, and the foot has a compact character 

 like that of Dicyncdon. 



The scapulae have the pre-scapula developed on the same plan as in 

 Cynognathus, and the anterior margin of the bone reflected upward, 

 so as to form the spine of the scapula, terminating in the acromion. 

 The two ends of the humerns are twisted at an angle of 45 degrees, 

 and the bone is expanded as in many Saurischian reptiles. The 

 carpus shows three bones in the proximal row, a large reniform 

 carpal below the ulna, regarded as the pisiform bone ; a compara- 

 tively small middle carpal is identified as the cuneiform bone. The 

 third bone corresponds with the scapho-lunar of Theriodesmus ; it is 

 beneath the radius. There is no indication of any pre-pollex. There 

 are four bones in the distal row of the carpus. There are five digits. 



In the pelvis and the limb bones this Anomodont type approxi- 

 mates to the Saurischia and Mammalia, just as the Ornithischia 

 approximate to birds in the same parts of the skeleton. 



Trirachodon is founded on four individuals which have the skull 

 about 4 ins. long. Like the other Gromphodont genera, this type has 

 the dentary bone developed so as to occupy the length of the 

 mandible, but the lower jaw is composite, the internal bones filling 

 the space which in mammals is occupied by the meckelian cartilage. 

 The post-frontal and pre-frontal bones are well developed. The 

 species differ in the character of the teeth, especially in number and 

 form of the pre- molars. 



In one species from Aliwal North, the molar teeth are transversely 

 wide, ornamented with three transverse ridges, which terminate in a 

 slight cusp, both on the external and internal margins. There are 

 not more than nine molars. The crown of the first pre-molar in one 

 specimen is elongated from front to back, and shows a small coronet 

 of rounded marginal cusps. In a species from Lady Frere the molar 

 teeth are narrower, and the pre-molar teeth more numerous, small, 

 and circular in the broken sections. 



Although these skulls are mammalian in aspect, and in some 

 respects make new transitions towards mammals, in technical 

 characters they retain a sufficient number of reptilian structures to 



