. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. THE SKULL 93 in which they are replaced functionally by strong horny sheaths on the edges of the jaws. The teeth may be borne on the palatine and pterygoid, as well as oil the maxilla, premaxilla (which is usually unpaired), ....a^^^Eic,-. and dentary. ^^V^^^^'^ In the young Hatteria only amongst existing Reptiles do the vomers bear teeth (usually one on each). In certain fossil forms brush- like masses of sphenoidal teeth were present. The remarkable horned skull of the gigantic GeratojMidce (Dino- sauria) which reach
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. THE SKULL 93 in which they are replaced functionally by strong horny sheaths on the edges of the jaws. The teeth may be borne on the palatine and pterygoid, as well as oil the maxilla, premaxilla (which is usually unpaired), ....a^^^Eic,-. and dentary. ^^V^^^^'^ In the young Hatteria only amongst existing Reptiles do the vomers bear teeth (usually one on each). In certain fossil forms brush- like masses of sphenoidal teeth were present. The remarkable horned skull of the gigantic GeratojMidce (Dino- sauria) which reached a length of nearly seven feet, possessed horny beaks in addition to teeth on the maxilla and dentary. A parietal foramen was present. In correspondence with the absence of branchial re- spiration during development, the branchial apparatus plays no great part in Reptiles, and often only the slightest traces of it arc seen: thus in Snakes, for instance, only the hyoid remains, and this not always. In Chelonians a basal piece (" basihyobranchial") as well as the first branchial arch per- sist in addition (Fig. 76).. Fio. 76.—Hyobbanchial Apparatus WITH Larynx and Trachea op Emj/s eiiro2XKa. ZH, basihyobranchial, which widens at ZB and bears the cricoid (RK) and arytenoid {AK) cartilages of the larynx; KH, lesser hyoid cornua; ZH, greater hyoid ooniua ; IK, first branchial arch ; Tr, trachea. E. Birds. The skull of Birds is formed on a similar plan to that of Reptiles—more particularly of Lizards, but it exhibits certain special characteristics (Fig. 77). The brain-case is proportionately very large, and all the cranial bones show a tendency to run together by the obliteration of the sutures originally present between them ; they are usually delicate and spongy (" pneumatic "), thus contrasting greatly with those of Reptiles.^ Only in the region of the nose does the cartilage persist throughout life to any extent, and even here not always. ^ It should, h
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
