614 PROF, H. G, SBELEY ON THE SKULL [May 26^ 



distortion of the specimen and is probably narrowed by a tenth- 

 of an inch. The teeth extend in diverging curves as they range 

 backwai'd and outward. The transvei'se width over the premolars- 

 in front is ^ inch ; over the last molars it is about 2^^ inches. 

 These measurements are less than in Diademodon broivni. Ten 

 teeth are indicated or preserved, of which the two in front, with 

 small circular fractured bases to the crowns, are classed as pre- 

 molars, and the eight succeeding teeth are molars. They have- 

 the crowns ti-ansversely ovate, each with its axis at right angles 

 with the concave external alveolar border, except the last tooth, 

 which is parallel to the alveolar border. The crowns increase in 

 width to the fifth molar and then become smaller, the seventh 

 and eighth rapidly narrowing acquire a triangular or comma 

 shape. The length occupied by the eight molars is l^f inch. 



The anterior teeth are separated by the hai'd palate between 

 them. They rise with a vertical inner alveolar border corre- 

 sponding to the compressed external border. As preservetl the- 

 hard palate is i-^ inch wide between the last premolar teeth, and 

 ■| inch wide where it terminates between the fifth pair of molars. 

 It is narrower than in D. brovmi, in which the fourth molar- 

 appears to be the largest. The hard palate as preserved is made- 

 by the maxillary bones, which extend behind the second molar 

 teeth, and unite by a transverse suture with the palatine bones, 

 so that the suture is in about the same position as in Gom2)ho- 

 gnathxis j^olyjjhagus (Phil. Trans. 1895, B, p. 16, fig. 7). Its. 

 distinctive feature is a strong elevated median ridge dividing the 

 palate into two concave channels. This ridge is continued back- 

 ward by what I regard as the vomerine bone, dividing the 

 posterior nares, extending upon the median union of the posterior- 

 palatine bones. This ridge on the hard palate is absent from 

 D. broivni ; its presence makes the transverse hinder border of 

 each half of the hard palate concave, instead of both bones 

 combining to form one concave posterior surface. The back of the 

 palate behind the posterior nares has a close general resemblance- 

 to the corresponding region of Gomphognathus. There are the 

 same pair of convex rounded tumid areas behind the hard palate 

 converging backward from the hinder cheek-teeth to terminate in 

 a pair of hemispherical convexities which were just in front of 

 the median post-palatal ridge in that genus, flanked externally by 

 the broken bases of the pair of transverse processes which 

 descended between the rami of the mandible (compare I. c. p. 24, 

 fig. 11). The transverse width over these processes in this speci- 

 men is ly'*^ inch. Those processes are regarded as being made 

 chiefly by the transverse bones and as defined by sutures which 

 converge inward from behind the maxillary bones laackward to the- 

 hemispheiical tubercles at the posterior fra,cture. 



The teeth have been more or less broken, possibly by strain or 

 compression. Small parts of the enamelled surfaces of the tuber- 

 culate crowns remain in the first and second molars of the right 

 side. The first shows a marginal external rim behind the crown 



