632 



PKOF. H. G. SEELEY ON THE KEPTILE 



pital is directed almost vertically downward, showing, I think, that 

 the head must have been carried upon the neck as in Deer, Kangaroos, 

 and other animals in which the position of the neck is vertical. The 

 part of the basioccipital posterior to the sella turcica is flattened on 

 its cranial surface, gently concave from side to side, with a slight 

 median ridge. Then at a distance forward of about 3 centim. from 

 the occipital condyle, the brain-case thickens from below upward, 

 but does not present the cup- shaped depression seen in Crocodiles 

 and many birds, though its edge is obviously destroyed by fracture, 

 and must have extended some millimetres higher than the 13 milli- 

 metres preserved. At the border of this ridge, on each side, is a 

 large perforation for the second nerve. The inner and anterior wall 

 of the perforation is broken away ; and the transverse width between 

 the outer walls of these foramina is 2 centim. Below these foramina, 

 and extending forward, are several others. First, on the right side 

 is a large foramen that runs obliquely outward and forward, pene- 

 trating into the brain-case. On the opposite side, instead of one 

 large foramen, there appear to be two, divided by a considerable 

 intervening piece of bone. I have no doubt that this foramen gives 

 passage to the fifth nerve. On the left side it is prolonged backward 

 and outward in a horizontal groove ; and although there is a groove 

 on the right side, and though it is smaller and shallower, it does not 

 impress the margin of the bone. In advance of this foramen, and 

 below the sella turcica, in the anterior concavity of the bone, are 

 two other foramina, which appear to be vascular. The anterior one, 

 owing to fracture, is seen on the left side to curve obliquely down- 

 ward and forward, and open upon the base of the skull. Between 

 the outlets of these foramina, in the median line, is a portion of a 

 conical foramen, the anterior wall of which is removed by the 

 fracture. 



The vertical fracture of the sphenoid (PI. XXVII. fig. 6), where it 

 terminates, is triangular, 2 centim. wide, and about as high, the sides 

 being compressed so as to meet superiorly in a crest which rises in front 

 of the pituitary fosse, as in some birds, and not at all as in Crocodiles. 

 Its walls are concave at the sides ; and posteriorly a slight longi- 

 tudinal ridge rises, which becomes directed at an angle inward and 

 upward to the ridge bordering the pituitary region behind. The pit 

 for the pituitary body is about 12 millim. long and 9 millim. wide, 

 is concave from side to side, and margined by a sharp elevated ridge. 

 Its anterior part is overhung by the process of the sphenoid, which 

 rises above it. The posterior portion of the lateral aspect of the 

 skull consists of a small superior area, subtriangular, formed appa- 

 rently partly of the parietal and partly of the supraoccipital bones. 

 It is a smooth internal surface below the fractured roof of the brain- 

 case, directed obliquely outward, downward, and forward, and 

 traversed by a groove which probably indicates a suture between 

 the two bones. The posterior border is a sharp knife-edge, concave 

 from before backward. Under this edge a deep excavation extends, 

 penetrating to within half a centimetre of the brain-case. The ex- 

 cavation is smoothly concave, extends longitudinally, and is pro- 



