On the geological position of the Castoroides ohioensis / by James Hall ; also a description of the cranium of the same, by Jeffries Wyman.

  • Hall, James, 1811-1898.
Date:
1846
Catalogue details

Licence: Public Domain Mark

Credit: On the geological position of the Castoroides ohioensis / by James Hall ; also a description of the cranium of the same, by Jeffries Wyman. 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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    the same foramen. In the Castors the central ridge extends backwards quite to the posterior edge of the palatine bones. The incisive foramen, which in the Castors, Ondatras, Mar- mots, Agoutis, &.C., acquires so great a size, is in the Casto- roides proportionally remarkably small, scarcely allowing the passage of an ordinary probe. The anterior edge of the first molar is situated just in the middle of the base of the skull, but in the other genera above referred to, it is always in advance of the same point. The alveolar portion of the intermaxillary, situated just below the nasal orifice, presents a deeply indented and roughened sur- face, serving for the attachment of the upper lip, doubtless unusually developed in order to conceal the large incisor teeth. The nasal orifice is more quadrangular, but otherwise resembles that of the Castors. The zygomatic arches project farther from the side of the cranium, but are much more slender than in the Castors, es- pecially behind the post orbitar process of the malar bone; the orbitar process of the frontal bone is small. The zygomatic process of the temporal is also more slender, and the groove or channel serving for the lodgment of the condyle of the lower jaw is destitute of the ridge on its outer border, which is so well marked in the Castors, Ondatras, and Capybaras. The infra orbitar foramen presents nearly the same conforma- tion as in the Castors, but is provided externally with only a very slight projection of bone. The right inferior maxilla alone exists, and is in a perfect condition excepting only the incisor tooth. Its length from the angle to the edge of the incisive alveolus is 7 inches, and its breadth from the top of the coronoid process vertically down- wards, 3| inches ; all the processes are remarkably developed, and indicate the existence of powerful masticatory muscles; inferiorly it is remarkably broad and almost flat, from 1.5 to 1.8 inch in breadth, and terminating posteriorly in a triangular sur- face, the apex of which is turned inwards; in these peculiar- 4