Structure and Affinities of the Endothiodont Beptiles. 273 



and splenial, and a small part of the angular and sur-angular. There 

 is a marked general resemblance between this jaw and that of 

 Endothiodon bathystoma, but the present jaw is of much lighter 

 build. The dentary has no doubt been anchylosed to that of the 

 other side, and the jaw has ended in front in a sharp upwardly 

 directed process. The upper border of the dentary as preserved 

 shows that portion which met the maxillary. Externally it has a 

 sharp ridge which was probably covered by horn in the living 

 animal. Within this ridge is a groove followed by another ridge. 

 The two ridges are 10 mm. apart. To the inner side of the inner 

 ridge lies the row of teeth. In the specimen the roots of only five 

 are preserved, but there appear to have been at least ten and possibly 

 eleven teeth in the row originally. The last, however, is rudi- 

 mentary, and the second last small. Owen considers there are nine 

 in the upper jaw. The lower part of the symphysis, and possibly 

 more than half, is formed by the well-developed splenial. The 

 splenial also forms about two-thirds of the inner surface of the 

 portion of the jaw between the symphysis and the lateral fenestra. 

 The anterior portion of the angular fits in between the splenial and 

 the dentary as in Endothiodon bathystoma. The anterior part of 

 the sur-angular articulates with the dentary above the lateral 

 fenestra. 



The following are the principal measurements : — 



Depth of jaw in posterior molar region 60 mm. 



Length of molar series (as preserved) 67 



Width of occipital condyle 37 



Depth of occipital condyle (in middle) 17 



Width between ex-occipitals 128 



Cryptocynodon simus, Seeley. 



This genus, which is closely allied to Esoterodon, is only known 

 by the type specimen which was discovered by Seeley at Molteno 

 Pass, in the Nieuwveldt range. Unfortunately the type specimen 

 consists of only the preorbital portion of the skull, and that in a bad 

 state of preservation. It shows the presence of a single row of 

 simple molars as in Esoterodon, with the addition of a small canine 

 in front of and to the outer side of the row of molars. The arrange- 

 ment of the palate is very similar to that in Esoterodon, the vomer 

 uniting with the posterior median process of the premaxilla as in 

 that genus, and the suggestion might be made that possibly this is a 

 very young specimen of Esoterodon uniseries, the small canine being 



