Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/273

 Now "ces deux petites preeminences " and the azygos process in the Oxford (Shotover) skull make it highly probable, I think, that the slender anterior nasals are really present in these Steneosaurs ; but the indistinctness of the sutures prevented their recognition.

Not remembering one crocodilian skull, fossil or recent, in which the maxillaries entered into the construction of the external nostril, I examined, with special regard to this point, the large collection of recent skulls in the British Museum, comprising more than fifty skulls, including every known species of the gavial, crocodile, and alligator types, and also all the skulls in the Museum of the Royal College of Surgeons ; and I did not find one where the maxillaries formed part of the opening of the anterior nostril. In every instance this was formed of the praemaxillaries alone, as in the Gavials, or by the praemaxillaries and the nasals. I could not find one example of a median process projecting forwards from the posterior border of the nostril formed of the praemaxillaries. Such a process always consisted of the anterior extremities of the nasal bones, which either entered the posterior border of the nostril in the plane of the external opening (in most alligators), or below this plane (in many crocodiles, where the junction of the praemaxillaries behind the nostril concealed and overlay the front ends of the nasals, which descended into the nostril beneath them). In some skulls the nasal process received a small accession from the praemaxillaries ; but this was always subordinate to it, and never reached beyond its base. In Gavials also (where the intermaxillaries alone enclose the nostril) these minute projections of the intermaxillae into the nostril were sometimes present, but they were dwarfed and in- significant.

Should my suspicions prove correct, and Sten. rostro-minor and the Oxford (Shotover) skull be found to have the slender nasals of Sten. Manselii, this last will still be distinguished from Sten. rostro-minor by the different proportions of its skull, and the number and the distribution of its teeth.

What are the two large triangular bones in Sten. Manselii which descend from the forehead to the middle of the snout ? Evidently they correspond to the bones marked a a, fig. 5, pl. x., 'Ossemens Fossiles.' They are, I imagine, the principal frontal, retaining permanently in the adult Steneosaur the median suture which primitively divides it in the embryonic crocodile. Attaining in the Steneosaur a very large size, the divided frontal thrusts aside the posterior ends of the nasals, and, uncovered by these, forms so large a part of the surface of the snout. Its excessive descent, however, is less than at first sight appears ; for it is well known that in existing crocodiles the frontal, which seems to end in front of the orbit, really only disappears from the surface here, and beyond this, hidden and overlain by the prefrontals and nasals, it stretches forwards a long distance — in Croc. vulgaris exceeding one-third of the distance between the orbit and nostril.