. Elements of comparative anatomy. Anatomy, Comparative. 462 C0MPAKAT1VE ANATOMY. In most Saurii (and in Chelys among the Ckelonii), as in the Birds, tke premaxillaB are fused together; in the latter they are distinguished by the possession of a long frontal process. Their size is correlated with that of the beak, the form of which is largely due to the share - B that they take in it. Tkey are rudimen- tary in tke Opkidii (Fig. 249, 0 Px) and small in tke Ckelonii. Tke max- illa therefore forms the greater portion of the boundary of the edge of the lower jaw (Mx); this bone is of great size in
. Elements of comparative anatomy. Anatomy, Comparative. 462 C0MPAKAT1VE ANATOMY. In most Saurii (and in Chelys among the Ckelonii), as in the Birds, tke premaxillaB are fused together; in the latter they are distinguished by the possession of a long frontal process. Their size is correlated with that of the beak, the form of which is largely due to the share - B that they take in it. Tkey are rudimen- tary in tke Opkidii (Fig. 249, 0 Px) and small in tke Ckelonii. Tke max- illa therefore forms the greater portion of the boundary of the edge of the lower jaw (Mx); this bone is of great size in tke Croco- dilini and Saurii, and very large in tke Opkidii, in wkick also it is capable of a large amount of move- ment. There is a lateral series of bones at- tacked to tke quad- rate. Tke first of tkese is tke quad- rato-jugal; tkis is absent in tke Opki- dii. In tke Saurii it is connected with tke quadrate at tke point wkere tkis bone is united to tke skull. It is continued forwards into a second piece, wkick is partly connected witk a post-frontal, and partly with a jugal wkick passes round tke lower edge of tke orbit. In Birds tke quadrato-jugal (Fig. 250, B Qj) is a slender piece of bone, wkick arises from tke side of tke mandibular joint of the quadrate. In tke Ckelonii and Crocodilini it is connected witk a larger portion of tke quadrate, and supports tke jugal, wkick aids in bounding tke orbit. In all cases tke lower jaw is articulated to tke quadrate, and is made up of tke same parts as in Fiskes, to wkick, kowever, a supra- angular and a complementary bone are added on. In tke Ckelonii and Aves tke two dentaries fuse very early; in Birds tke otker bones retain indications merely of their primitive. Fig. 251. View of the base of the skull. A Of Chelonia. B Of Crocodilus. Ob Basi-oceipital. 01 Exoecipital. C Occipital condyle. Spb Basi-sphenoid. Qpo Opisthotic. Pi Pterygoid. Pal Palatine. Vo Vomer. Q Quadrate. Qj Quadratojngal. Tr Transverse. Mx Maxilla. Pa Pre- inax
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
