On the anomodont Reptilia and their allies / by H.G. Seeley.

  • Harry Govier Seeley
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: On the anomodont Reptilia and their allies / by H.G. Seeley. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    palato-nares. The lateral excavation shows the palatine plate to extend upward and inward as in other specimens. The distorted condition of the specimen makes detailed measurement of little value. The liead is about 13 centims, long, and the height of the vertical face is about 8‘5 centims. from the cutting margin of the jaw to the flattened frontal region. The circular nares are rather above the middle of this height; each is 2 centims. in diameter, and the bar which divides them, formed by the nasal bones above and the pre-maxillary bone below, is half a centim. wide. The pre-maxillary bone is extremely narrow (about 2 centims.), and may be divided by a median suture, though the state of preservation does not demonstrate this point, and the appearance may be delusive. The circular orbit is 4 centims. in diameter; the malar bone extends internally to the post-frontal at its hinder border, and both bones are overlapped externally by the squamosal, which at once rises to a level with the crown of the head as it extends backward. At the back of the head is a slender sigmoid bone, expanded at both ends, about 9'5 centims. long, which may be the clavicle. These characters amply establish the distinctness of this species, and make its reference to a distinct genus not improbable; but I do not regard the vertical opposi- tion of the pre-maxillary and mandible on which Lystrosauriis was founded as a suflicient definition of the genus. The Skull of Hyorhynchus platyceps, Seeley. (Plate 15, figs. 1-3.) A skull, which is imperfect both in front and behind, registered in the British Museum as B. 872, received from Mr. Thomas Bain, is so remarkable in its form that I regard it as probably indicating a new genus. It is characterized by a slender angular Pig-like snout, relatively large orbits, and a narrow parietal region. The upper surface of the head is flattened, slightly convex from front to back in the median line, with the superior borders of the orbits somewhat elevated, so as to make the frontal bones between them longitudinally concave. The post-orbital region has a ' length of 3 centims. as preserved, and is about 12 millims. wide at the posterior |j fracture, where a transverse section shows that it is the summit of a verticallv ovate ii region of the brain-case. As in so many other allied forms, its lateral w’alls diverge j] outward as they extend forward to the posterior angle of the orbit, where the post- ;j frontal bone extends transversely outward. The post-frontal is very slender. It is || directed at first outward and downward, and then downward and forward, making the ij posterior boundary of the orbit. This aperture on each side of the head looks outward jl and a little upward, is 4 centims. long, by 3’3 centims. deep. The width of each |] frontal bone from the median suture to the orbital border is P6 centim. in the middle of | the orbit. The sutures are badly defined. The parietal appears to be overlapped by the post-parietal bone, which extends forward to the post-frontal, and has the side ! flattened and obliquely inclined. At about 1‘5 centim, behind the orbits is the long