Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/128

30 Twenty-one teeth occupy a space of 8 inches. The length of a fang slightly exceeds ⋅3″, the diameter (including the capsule) averages ⋅3″, and that of the dentinal cylinder minus its investing capsule ⋅15″. The apices of all the crowns are broken off, so that the entire length of the teeth is not determinable.

In their form and structure these teeth repeat so closely the characters of those of the Kimmeridge Enthekiodon as to suggest the great probability of their both belonging to the same genus. My note on Enthekiodon, communicated last session, noticed the resemblance of its teeth and of the mode of their attachment to the jaw to those of Ichthyosaurus; but my material was too imperfect to justify me in certainly referring it to that genus. I have now, however, indisputable evidence that it is a true Ichthyosaurus; and this being so, the similarity of the dental characters of this Gozo mandible to those of Enthekiodon affords a strong presumption that it also is Ichthyosaurian.

The skull is in form elongated and sub triangular. Its sides converge regularly from the posterior and outer angles of the quadrate bones to the 8th tooth, counted from behind. From this they are nearly parallel, to the 14th tooth, in front of which the snout is slightly contracted where the premaxillo-maxillary suture crosses its alveolar border. The end of the snout, including the external nostril, is wanting.

The syncipital area is a nearly flat oblong, measuring transversely along its posterior border 5″⋅4, along its anterior border (a line connecting the anterior and outer angles of the postfrontal bones) 5″, and from front to back 3″⋅2. The entire surface of this area is symmetrically pitted. In its frontal part, which is hollow transversely and plane axially, the pits are grouped in lines diverging from the axis of the skull, and there is a large remarkable pit in each posterior angle of the area.

The supratemporal fossæ are very large, and have an angulated pentahedral shape. Their transverse diameter, slightly larger than the others, is 1″⋅8. The intervening parietal bone has a minimum width under ⋅1″.

The interorbital space is narrow, hollow transversely, plane axially, and less strongly pitted than the syncipital area.

The orbits are large, their contour is subtriangular, incomplete behind; they look directly upwards; and their long diameter is directed from behind forwards and inwards. The outer, front, and inner part of their margin is raised; and the front part is channelled by two grooves, of which one descends longitudinally on the prefrontal bone, and the other along the junction of the prefrontal and lachrymal bones.

The nasal bones posteriorly reach the level of a line joining the anterior angles of the orbits, and, descending the snout in the form