File:Image from page 132 of "On the anatomy of vertebrates (electronic resource)" (1866) (14753153184).jpg

Identifier: b20416039_001 Title: On the anatomy of vertebrates [electronic resource] Year: 1866 (1860s) Authors: Owen, Richard, 1804-1892 Subjects: Anatomy, Comparative Vertebrates Fishes Reptiles Mammals Birds Publisher: London : Longmans, Green Contributing Library: Wellcome Library Digitizing Sponsor: Wellcome Library

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Text Appearing Before Image: ehind, but distinct from, the tympanic. In the Lepidosiren the ali- and orbito-sphenoids and the hypo-tympanic remain cartilaginous;premaxillaries are representedby their ascending or facialparts coalesced into a singleplate, supporting the two pre-hensile teeth. The postorbito-supertemporals, fig. 41, 12, are( dermal or scleral bones, over-lapping the fronto-parietals.They are not present in modern Batrachia. In the Axolotl (Axolotes marrnoratus), the basioccipital is repre-sented by the posterior part of the common broad and flat basi-cranial bone. The exoccipitals are separated below by this process,and above by a cartilaginous representative of the superoccipital.Each exoccipital developes a small, almost flattened condyle,anterior to which it is perforated by the eighth pair of nerves ; itarticulates above with the parietal and mastotympanic, and isseparated from the alisphenoid by the large cartilaginous petrosal,to which a small discoid representative of the stapes is attached,

Text Appearing After Image: Hyo-branchial frame, skull, older Tadpole, cxxxi . 88 ANATOMY OF VERTEBRATES. closing the homologue of the 6 fenestra ovalis. The basi-sphenoidal portion of the basicranial plate sends ont an angularprocess on each side, which supports the alisphenoid. Thesurfaces of the alisphenoid are directed forward and backward,instead of from side to side, and it constitutes chiefly the anteriorparietes of the otocrane; the inner and anterior border isnotched by the great trigeminal nerve. The parietals are longand broad, divided by the sagittal suture, and impressed at theposterior and outer angle by the anterior attachment of the greatdorsal trunk-muscles. The masto-tympanic is articulated to thispart of the parietal and to the exoccipital; it includes all thedivisions of the pedicle save the lowest, 6 hypotympanic, whichaflbrds the articulation to the mandible. The orbitosphenoidsare divided by an unossified tract of some extent from the ali-sphenoids, and articulate above with the extremity

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