1908.] ON THE SKULL OF THE FOSSIL REPTILE DIADEMODON. 611 



5. Additional Evidence as to the Dentition and Structure of 

 the Skull in the South African Fossil Reptile Genus 

 Biademodon. By H. G. Seeley, F.R.S., F.Z.S., King's 

 College, London. 



[Received May 26, 1908.] 

 (Text-figure 130.) 



The genus Diademodon was founded on the molar teeth and 

 imperfect middle portions of small skulls. Four species were 

 figured in Phil. Trans. Royal Society, 1894, B, pi. 89, referred to 

 D. tetrago7ius, D. brachytiara, D. mastactts, and D. hroio')d. They 

 were the most remarkable evidences of dentition of mammalian 

 type in extinct reptiles which have heen found in South Africa. 

 There would have heen grounds, had the remains been mammalian, 

 for referring them to three genera ; and in the description of 

 plate 89, figure 11 is described as the left maxillary region of 

 Biademodon (or Gomphognathus) mastacus. And in the original 

 description of JD. hrowni {I. c. p. 1039) it is observed, "it is 

 probably the type of a distinct genus." Later in the same year 

 the group Gomphodontia was defined as comprising animals with 

 a Theriodont type of dentition, in which the molar teeth are 

 expanded transversely, and as having more or less tuberculate 

 crowns, of the type shown in Diademodon. In that group the 

 genus Diademodon was included {I. c. 1895, B, p. 3). The types 

 of Gomphognathus had the crowns of the molar teeth well worn, 

 but the elevation of the external cusps or ridge in G. polyphagus 

 made a suggestive resemblance to Diademodon mastacus ; while 

 the condition of the single well-preserved crown in Diademodon 

 broioni makes an equally suggestive approximation to Diademodon 

 hrachytiara. In 1896, in a short communication to the British 

 Association at Liverpool, I briefly noticed another skull discovered 

 by Dr. D. R. Kannemeyer. I have removed the matrix in the 

 laboratory of King's College, so as to demonstrate the sutures in 

 the middle part of the skull and to expose the palate. The 

 specimen is slightly squeezed so as to have a lateral obliquity 

 towards the right side, from which the similar example of 

 Diademodon broumi is not free. There is a coincidence in the 

 anterior and posterior fractures being in identical positions in both 

 specimens, favouring comparison. They are closely related species, 

 but the snout in the new example is narrower and rather smaller, 

 and the dentition being unworn favours the idea of specific 

 difference, though the forms of the transversely ovate sections of 

 the molar and premolar teeth are almost identical. 



As preserved the specimen is 2^ inches long. It extends 

 between an anterior transverse fracture through the two concave 

 pits on the snout, which lie at the junction of the maxillary and 

 nasal bones, which in Gomphognathus are situated midway between 

 the orbits of the eyes and anterior nares, and a posterior fracture 



