Structure and Affinities of the Endothlodont Reptiles. 271 



Width of parietal crest 29 mm. 



Width of back of skull 324 



Width of mandible at back of dentaries 117 



Greatest width of humerus 98 



Length of four sacral centra 95 



Length of iliac crest 125 



Length of ilium 154 



ESOTERODON UNISEEIES (Owen). 



This Endothiodont reptile was described by Owen in 1879 (5) 

 from a snout sent to the British Museum by Mr. T. Bain. Though 

 Owen in his paper does not give any locality for the specimen, in 

 the British Museum Catalogue (1890) Lydekker (4) states that the 

 specimen came " from the Beaufort beds on the flanks of the Nieuw- 

 veldt range." The specimen consists of the anterior part of a skull 

 which bears some resemblance to that of Endothiodon bathystoma, 

 but differs, among other things, in only having a single row of teeth. 

 Owen described it under the name Endothiodon uniseries, and, com- 

 paring it with Oudenodon and Dicynodon, concluded that " the 

 cranial characters are Anomodont." The row of teeth Owen appears 

 to have regarded as belonging to the palatine bone, and the real 

 palatine bone he looked upon as the pterygoid. Lydekker pointed 

 out Owen's error, and gave what is no doubt the correct interpreta- 

 tion of the bones. 



Seeley in 1895 (2) regarded the fossil as the type of a new genus, 

 and though there is no doubt that it is closely allied to Endothiodon, 

 I agree with Seeley in placing it in a distinct genus. 



In 1900 I published a restoration of the palate, and showed the 

 structure and relations of the vomer. 



With the exception of the type specimen no other remains have 

 hitherto been known. In the collection of fossils obtained by Mr. T. 

 Bain, and recently presented to the South African Museum by his 

 son, Mr. J. M. Bain, there are two specimens which almost certainly 

 belong to this form. The first of these is the anterior portion of the 

 left mandible. It not only belongs to this species, but it is in the 

 highest degree probable that it is the mandible of the same indi- 

 vidual. Most likely Mr. T. Bain found the jaw at the same time as 

 the snout, and when sending the snout to the British Museum ap- 

 parently omitted to send the jaw — possibly thinking the snout was 

 all that was required to determine the form. The second specimen 

 is the crushed occiput and posterior part of the base of the skull. 

 This is also almost certainly a part of the skull of Esoterodon 



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