612 PROF. H. G. SEELEY ON THE SKULL [May 26, 



behind the orbits, just behind the post-frontal bones, which are 

 imperfectly preserved. The lateral margins converge foi-ward in 

 a wedge-like oittHne similar to the corresponding part of the 

 skull of GomphognathiLS. Owing to the lateral compression the 

 anterior transverse measurement is narrowed by one or two tenths 

 of an inch. As preserved it is one inch wide, and the vertical 

 height from the median longitudinal ridge on the palate to the 

 nasal bones is the same. The corresponding measvirements in 

 Diademodon broioni are : vertical 1^, transverse 1 j^q inch. The 

 pre-orbital lateral areas of this, formed chiefly by the maxillary 

 bones, are inclined towards each other, are gently convex from the 

 alveolar border to the nasal region, longitudinally furrowed by two 

 shallow concavities on each side, and then round with a gentle 

 convexity into the upper surface formed by the nasal bones. 



Diademodon hrowni distinctly suggests an angle between the 

 sides of the face, which are more vertical, and the roof of the 

 snout ; but the difference between the specimens is one of degree. 

 In both there is some lateral concavity of the pre-orbital region 

 from front to back. 



The head widens backward to the posterior fracture, which 

 passes through the back of the frontal bone, the post-frontal 

 bones, and the pterygoid bones. The specimen is about 2 j^ inches 

 wide behind the dentary tract, which is in a line with the middle 

 of the orbits, and 1^ inch high at the back of the frontal 

 bones. 



The bones seen on the superior aspect of the skull are the 

 frontal, post-frontal, pre-frontal, nasal, lachrymal, and maxillary. 

 The naso-maxillary region is convex from side to side, but as the 

 nasal bones extend between the orbits their flattened upper 

 surface merges in the flattened frontal region. The orbits are 

 inclined so to look outward, and to a less extent upward and 

 forward. The vertical measurement of the rounded cavity is one 

 inch, and the transverse measurement between them over the pre- 

 frontal bones is 1^ inch. In D. brotvni it appears to have been 

 1^ inch. 



Only the part of the post-frontal bone which is above the back 

 of the orbit is preserved. It is rather less than half an inch wide 

 between the temporal vacuity and the suture with the pre-frontal 

 bone. It is transversely channelled owing to elevation of its front 

 and back borders. These bones are slightly raised above the 

 frontal bones, which extend longitudinally between them. As 

 preserved the frontal bones are oblong, -jSg- inch long, and more 

 than half an inch wide towards the middle at the suture between 

 the post-frontal and pre-frontal bones, and narrow anteriorly to 

 the transverse suture with the nasal bones. Both bones are 

 longitudinally concave with the median sutural line raised. This 

 feature is absent in Diademodon hrowni. The lateral sutures with 

 the post-frontal and pre-frontal bones are similarly raised as slight 

 ridges, but there is no ridge between the frontal and nasal bones. 



The pre-frontal bone forms much of the superior border of the 



