630 



PROF. H. Gr. SEELET ON THE EE P TILE 



in somewhat close contact with the nenral arch of the atlas, and for 

 the transverse grooves and muscular rngosities, which run between 

 this border and the slight groove denning the supposed cranial scute. 

 Hence the back of the skull is not vertical, like that of some Croco- 

 diles, and its superior margin is far from being as well rounded as in 

 very young Crocodiles ; and on the whole there is nothing to call for 

 remark as affiliating this region to what is seen in either Crocodiles 

 or Lizards. The surface ascends somewhat obliquely, but in two 

 terraces ; that immediately above the ridge bordering the foramen 

 magnum is divided by it into two lateral portions. These lateral por- 

 tions are channels extending outward and downward, and widening 

 as they go. There are, on each side of the median vertical dividing 

 ridge in these channels, three large tubercles. Above the channels, 

 and as nearly as may be of corresponding size, is a pair of convex 

 surfaces, which are undistinguishable in the middle from the median 

 bar just referred to. They are margined above by the supposed 

 cranial scute, and, as they extend outward, widen and curve obliquely 

 upward ; and a muscular ridge appears dividing the outer part of 

 this wedge longitudinally into two nearly equal parts. Hence the 

 pattern of the back of the skull as preserved is very like a capital 

 letter K placed transversely, so that the two diverging limbs corre- 

 spond to the ridges above the foramen magnum. The height from 

 the top of the foramen magnum to the summit of the back of the 

 skull is 2 centim. The transverse width over the supraneural ridges 

 is 4 centim. The width of each ridge at its outer third, before its 

 upper border becomes concave, is 9 millim., the upper margin extend- 

 ing over the concave channel above it ; higher up its width is little 

 more than half. The median connecting ridge between the two 

 transverse ridges at the back of the head is about 12 millim. wide. 

 Though the back of the head as a whole is convex from side to side, 

 it is concave from above downward in the median line. The foramen 

 magnum is slightly elliptical, being 17 millim. wide and about 15 

 millim. high. The skull presents the unusual condition that the 

 basioccipital condyle retreats below and in front of the upper border 

 of the foramen magnum, so that, placing the back of the skull verti- 

 cally, which puts the base of the skull horizontal, the back of the 

 brain-case projects for a centimetre behind the basioccipital condyle. 

 The areas at the outer and upper corners of the occipital condyle 

 are concavely notched, and at first convex from side to side, but 

 more flattened as they pass outward and upward. The depth from 

 the back of the skull to the base of the occipital condyle is 4 centim. 



The base of the skull, as preserved, is triangular, 5-J centim. 

 from the hinder border of the foramen magnum to the front of 

 the basisphenoid, or a fracture in front of the sella turcica. The 

 hinder border of the triangle is convex, and the lateral border is 

 concave, though all the borders are irregular. There is no sutural 

 distinction between the basioccipital and basisphenoid, any more 

 than between the basioccipital, exoccipitals, and supraoccipital bones. 

 The basioccipital condyle probably is formed to some extent by the 

 exoccipital bones, much as in the Crocodile, since foramina occur 



