636 



PKOE. H. G. SEELET ON THE EEPTILE 



been six (fig. 7). These foramina are different from those of Struthio- 

 saurus or Iguanoclon, and furnish a marked character, defining Acan- 

 thopholis. It may be difficult to correlate them with the foramina in 

 the back of the skull of a Crocodile ; but since those perforations are, 

 for the most part, in the exoccipital bones, and extend downward at 

 the back of the skull, it is obvious that we have here in the longitu- 

 dinal arrangement something more nearly paralleled by Lizards,where 

 the twelfth, eleventh, tenth, eighth, fifth, and second nerves are given 

 off in more or less longitudinal series. The hindermost foramen 

 may be referred to the hypoglossal nerve, the next, perhaps, to the 

 pneumogastric nerve, then perhaps a vascular foramen. The two 

 hinder foramina are much smaller than the third ; and the third 

 foramen may probably be for the eighth nerve ; the fourth is sma]l ; 

 the fifth is so large that it might well correspond to the fifth nerve. 

 The anterior direction of the sixth makes it probable that we have 

 here the foramen for the optic nerve ; for though it is somewhat 

 smaller than might have been expected, it is given off from the most 

 anterior part of the side of the brain-case behind the sella turcica. 



The anterior extremity of the basisphenoid is massive and wedge- 

 shaped, broken away on the compressed inferior lateral margins, as 

 well as in the front. A strong vertical plate rises in the middle, so 

 as to form the anterior border of the brain-case (fig. 8). The upper 

 margin is 3| centim. above the base of the skull, and it is nearly 

 2 centim. behind the anterior fragment of the basisphenoid preserved. 

 This plate therefore seems to me to be exactly in the position of the 

 posterior border of the sella turcica ; but if so, the anterior border, 

 such as is seen in Struthiosaurus (figs. 6, 5), is entirely broken away. 

 What remains of the sella turcica is a concave base in front of the 

 plate, terminating anteriorly in two diverging concave streaks of 

 bone-surface, which probably represent the channels of the caro- 

 tids (fig. 8). They extend downward and outward, making an angle 

 of 90° with each other, and do not appear to reach forward. On 

 each side of the posterior plate of the sella turcica there is a con- 

 cave notch in the skull-wall. 



The skull diverges so far from both the Crocodilian and Lacertian 

 types that it may be as well to recognize it as equally distinct from 

 both. It resembles Struthiosaurus in the downward direction of 

 the occipital condyle, in the extension of the lateral wall of the 

 brain-case posterior to the condyle, in the transverse horizontal ex- 

 pansion of the exoccipital region in front of the occipital condyle, 

 in the massiveness of the bone in the auditory region, and in the 

 grouping of the foramina, so that the posterior three are inferior, 

 while the anterior three have a more anterior and lateral position : 

 but the convex form of the base of the occipital bone, the immense 

 thickness of the basisphenoid bone, are matter for distinction, as is 

 the form of the alisphenoid in Aeanihopholis. The resemblances, 

 however, are so remarkable as to show that these two genera are 

 near allies ; and though we cannot infer with certainty the roof of 

 the brain-case of AcanthopJiolis from that of Struthiosaurus, or the 

 teeth of Struthiosaurus from those of Acanthopholis, yet they seem to 



