Structure And Development Of The Skull

Author : William Kitchen Parker
Publisher : Theclassics.Us
ISBN 13 : 9781230347240
Total Pages : 24 pages
Book Rating : 4.3/5 (472 download)

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Download or read book On the Structure and Development of the Skull in Sturgeons written by William Kitchen Parker and published by Theclassics.Us. This book was released on 2013-09 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1882 edition. Excerpt: ... exactly like it, but gently bent in the opposite direction; its teeth look a little forwards and fit in between those of the upper jaw. The palatine (Plate 14, fig. 5, pa.) is a styloid tract of bone binding on the external edge of the broad fore part of the suspensorium (pg.q.)', it is edentulous. The pterygoid (fig. 5, pg.) carries teeth; it is a thin plate of bone, which lies inside the hinder convex edge of the cartilage. Over the rudimentary "orbitar process" of the suspensorium a small scale of bone is visible, just as when the squamosal is formed over the quadrate in the Amphibia this is the preopercular (p.op.). In the roof and sides of the pharynx inside the first branchial arch there are three pairs of small, arcuate, dentigerous scales of bone (Plate 13, fig. 12, and Plate 14, fig. 5); these are "upper pharyngeal bones." Clamping the hinder part of the hyomandibular, its rudimentary "opercular process," the opercular bone (op.) is seen; it is a convex shell, with spurs in front and a sharp round margin behind. These bones are evidently all mere parostoses; the "ectosteal" sheaths of the visceral arches have not appeared yet; the cranium never acquires any well-grafted bony plates. Third Stage (continued).--Horizontal sections of one of the lesser larva of Acipenser ruthenus, at this stage--13 millims. long. Section 1.--The uppermost of these sections (Plate 13, fig. 10) is through the hemispheres and the base of the mid-brain directly over the thalamencephalon (Cla., C1.), the eye-balls (e.), and the front and sides of the mouth (m.). The quadrate and pterygoid regions (q., pg.q.) are severed, being cut through where there is a depression above; moreover, the broad pterygoid plate is obliquely placed, and thus this horizontal...