Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/271

 Shotover exactly correspond with those figured in the ' Ossemens Fossiles.'

So far, then, as regards the proximal half of its snout, this Kimmeridge Steneosaur apparently agrees with the Honfleur Gavials, and with the Oxford (Shotover) Steneosaurian skull, in the presence and in the relations of this pair of large triangular hones. The distal half, however, is differently constructed; for in the Kimmeridge Steneosaur Cuvier's large triangular nasals are preceded by a pair of distinct slips, which are intercalated first between the maxillaries, afterwards between the intermaxillaries, and which finally enter the posterior border of the external nostril, where they form a low mesial projection, on each side of which is a vertical groove. The posterior ends of this mesial pair of slips taper acutely; and, diverging widely, they embrace for 3-5 inches Cuvier's large nasals, having these on their inner edge and the maxillaries on their outer border. Between the point where they diverge and the external nostril, a distance of nearly six inches, their inner borders meet in the middle line ; and their width averages "9 inch, decreasing slightly towards the nostril.

This is an important difference : the external nostril of our Kimmeridge Steneosaur is not completely enclosed in the praemaxilla as in the Teleosaurs and recent Gavials, and as it is described in the Honfleur Gavials and the Oxford (Shotover) Steneosaurian skull, but its posterior border contains another element, the anterior ends of a mesial pair of bones, the distal six inches of which have the same relations to the maxillaries and intermaxillaries and to the nostril as the nasals in the crocodiles and in the alligators.

The nostril is subterminal, oval, the larger end behind. Its opening, directed upwards, is indented in the middle line, in front by the praemaxillary symphysis, and behind by the ends of the slender nasals ('?), as just described.

The praemaxillae ascend 2.2 inches behind the nostril, wedged in between the maxillaries and slender nasals. Their inner border, touching the latter, is straight. The suture which joins their outer border to the maxillary is oblique ; it crosses the dentary margin of the snout just in front of the fourth alveolus.

There are seventeen alveoli on each side ; the hindmost one visible, in the left side, is so small that it is almost certainly the last ; but since the edge of the jaw is deficient behind it, I cannot be absolutely sure of this. The first three teeth are contained in the praemaxilla ; and the interval between the third and the fourth tooth is rather wider than those between the rest.

The teeth, some of which are still in the sockets, while others are scattered loose over the palate, correspond with those of the lower jaw, and therefore do not require description. Their size and figure vary within rather wide limits, as they do in many living crocodiles^ but the essential features are constant.

The palatine plates of the praemaxillaries and of the maxillaries, and the inner edges of the palatine bones (so far as these latter are preserved), join in the middle line, and make the bony palate very

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