. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. REPTILES. 309 The vertebrae are mostly procoelous, but some of them may have plain faces. There are two sacral vertebras. The position of the girdles inside the ribs is secondary, and is produced during growth by the forward and backward ex- tension of the carapace. The ribs have but a single head, and extend into the caudal region (Fig. 15 5^- The procoracoid is fused to the scapula, the carpus is primitive, but the tarsus is modified by fusion of its ossicles. Five digits always occur, but the number of phalanges is not co
. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. REPTILES. 309 The vertebrae are mostly procoelous, but some of them may have plain faces. There are two sacral vertebras. The position of the girdles inside the ribs is secondary, and is produced during growth by the forward and backward ex- tension of the carapace. The ribs have but a single head, and extend into the caudal region (Fig. 15 5^- The procoracoid is fused to the scapula, the carpus is primitive, but the tarsus is modified by fusion of its ossicles. Five digits always occur, but the number of phalanges is not constant. The brain has large hemispheres which cover the twixt and partly the mid brain ; the cerebellum is a slightly arcuate trans- verse fold. The facialis and acusticus nerves are united at their origin. Both Harderian and lach- rymal glands occur, the latter being at the poste- rior angle of the orbit. Fig. 306. ?^Vv\\oi\.m<i\&,Chrysemyspicla. T^i . â 11 J /', basioccipital; f, frontal; eo, exoccipital; ;', The tympanum is well de- . , â , \ r . 1 â ' ^ jugal; in, maxillary; np, naso-preirontal; veloped, the membrane is /, parietal; pf, postfrontal; /;f, pterygoid; q, visible externally, and the quadrate; s, squamosal; io, supraoccipital. Eustachian tube is large. The ventricular septum is poorly developed; the third aortic arches are not connected with the radices aortae, and the left radix gives off the coeliac artery before joining with its fellow. A renal portal system is lacking, the caudal vein connecting with the epigastrics. The sexual and urinary ducts empty into the neck of the urinary bladder. The penis is an unpaired structure arising from the dorsal wall of the cloaca, and in it are two canalicular extensions of the ccelom, which open on two papillas to the exterior. The eggs are covered with a leathery calcareous shell, and are buried in the sand, being hatched by the heat of the sun. Some of the chelonia are herbivorous, some feed on insects, mollus
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