1908.] OF THE FOSSIL REPTILE DIADEMODON. 613 



orbit where the margin is compressed posteriorly and rounded in 

 front. The bone is in front of the post-frontal, external to the 

 frontal, makes an oblique suture with the nasal, and a narrow 

 junction with the lachrymal bone, as its sutural junctions diverge 

 outward and forward. It is | inch long from the post-frontal to 

 the lachrymal and -^ inch wide at the fronto-nasal suture, where 

 it is widest in about its middle length. The inner short border 

 next the frontal is parallel to the longer external border above the 

 orbit and lachrymal. The pre-frontal bone forms a large part of 

 the internal anterior wall of the orbit. 



The nasal bones, somewhat lanceolate in form, are imperfect 

 anteriorly. They extend from the frontal bones forward as 

 preserved to between the pair of pits on the front of the snout, 

 which are not seen in Diademodon hroioni, with a length of 

 Ij^Q- inch, and in this length they are not in contact with the pre- 

 maxillaiy bones. They ai-e separated from each other by a fine 

 straight suture, and widen from the frontal suture anteriorly, with 

 the lateral divergence of the sutures dividing them from the pre- 

 frontal and lachrymal bones, to 1^ inch at the front of the 

 lachrymal bones ; and anteriorly the sutures between them and 

 the maxillaiy bones converge forward, to a transverse width over 

 the nasal bones of half an inch, at the anterior fracture throughi 

 the lateral-nasal pits. The bones are smooth, convex from side 

 to side, and slightly raised posteriorly, with a partial prolongation 

 forwai'd of the median frontal sutural ridge. 



The lachrjanal bone is best exposed on the left side, where I 

 have partially removed the matrix from the orbit. It is at the 

 front of the orbit between the maxillary bone below and the nasal 

 and pre-frontal bones above. Externally it is of irregular sub- 

 quadrate form, half an inch in each measurement. It has a 

 considerable extension in the front of the orbit internally, below 

 the pre-frontal bone. On the lower part of the inner front border 

 the bone is pierced by two circular canals placed one below the 

 other. 



The maxillary bones form the sides of the face from the hinder 

 fracture at the back of the alveolar tract below the orbit, whei'e 

 the bone is y^ inch deep, forward to the anterior fracture, where 

 the depth is l^-(^ inch. The ascending orbital border below the 

 orbit is compressed, rounded, and slightly reflected outward. 

 Below the lachrymal canal the depth to the alveolar border is 

 il inch. A slight wide shallow concavity extends longitudinally 

 forward, from the oi'bital junction between the lachiymal and 

 maxillary bones ; but on the right side the bone appears to be 

 accidentally impressed in this region. The lower part of the 

 maxillary bone is moderately concave in length, and markedly 

 convex downward owing to the compression of the bone imme- 

 diately above the molar teeth. On the convex ridge above are 

 two ovate foramina above the teeth, such as occur in many fossil 

 reptiles. 



The palate has shared in the side to side compression and 



