Vol. 56.] DICRANOZYGOMA LEPTOSCELUS. 649 



summit of the postfrontal arch to the orbit, as a thin bar external 

 to the relatively small malar bone. Its extreme length exceeds 

 o inches. The short temporal vacuities are half as wide again 

 as long, but are inclined obliquely outward and forward ; while the 

 orbits must have been directed obliquely inward and forward. 

 On these data I have restored the skull in the accompanying 

 figure (p. 648), basing the form and length of the snout on known 

 characters of allied reptiles. 



The Vertebral Column. 



The total length of the vertebral column, as preserved, is 1 8 inches 

 from the occipital plate to the last sacral vertebra. It extends in a 

 curve convex towards the right side — which has had the effect of 

 crushing the dorsal ribs together, so that they are all turned upward 

 on the right side to expose their external edges and vertically- convex 

 contour, corresponding to the natural curvature of the side of the 

 animal. On the left side the ribs are pressed flat in the usual waj , 

 curving outward so as to expose their posterior aspect. 



In the middle part of the column the specimen showed a natural 

 mould of the neural canal, and this, in the relief-cast, is now 

 shown as a canal, remarkable for its width and depth, which 

 diminishes somewhat in size as it extends backward. This preserva- 

 tion of the neural canal is the cause for the imperfect exhibition of 

 the forms of the neural spines of the dorsal vertebrae, which could 

 not in all cases be completely cleared in the anterior and middle 

 portions of the column, though I endeavoured to show the forms of 

 several on the right side of the slab. 



The cervical region has suffered from the effects of one of those 

 explosions which so frequently disturb the natural relations of bones 

 after death, so that the vertebrae are scattered, and the number of 

 cervical vertebras cannot be given with certainty. Effects of this 

 disturbance are also seen in the curvature of the backbone, the con- 

 dition of the skull, and other displacements of the bones. 



1 am unable to recognize more than six cervical vertebrae, 

 which are all scattered and imperfectly exposed. One of these, having 

 the centrum more than J inch long, exposed laterally, shows the 

 articular face of the centrum ; it is transversely ovate, § inch deep, 

 J inch wide, and is concavely cupped, exactly like the centrum of 

 Anfhodon. This fish-like form of articulation is the more interesting, 

 because there has hitherto been no evidence of it in the centra 

 of South African Theriodonts. The vertebra which is hindermost 

 in position appears to have flattened blade-like ribs which are convex 

 in front, straight behind, | inch wide, and three to four times as long. 

 The neural spines in the neck are vertical, but do not appear to 

 have been elevated. The scattered neck-vertebrae are on a slightly 

 lower level as compared with the dorsal vertebrae, which are in con- 

 tinuous sequence. But the earliest of these vertebrae are depressed 

 out of sight, together with the earlier ribs of the left side, the 

 scapular arch, and limb. 



Twenty-one vertebrae in advance of the ilium are indicated by 



