266 ZOOLOGY sect. 



four short, taporing dir/its, directed forsvards. The hind-limL is o{ 

 great size; in the usual squatting posture the thigh is directed 

 downwards, outwards, and forwards from the thigli-joint, the 

 slianlv inwards, backwards, and upwards from the knee. 'Yhefoot 

 consists of two parts, a tarsal refjion directed downwards froili the 

 heel-joint, and ^we long, slender digits united by thin folds of skin 

 or vjehs. T!uis the limbs are placed in such a way that the elbow 

 and kne3 face one another, and the first digit — that of the hand 

 probably representing the index-finger, that of tlie foot, the lirdlnx 

 or great toe — is turned inwards or towards the median plane of 

 the body. 



The skin is greyish-brown in R. temporaria, greenish in R. 

 esculenta, and is mottled, in both species, with dark brown or black ; 

 in R. temporaria there is a large black patch over the tympanic 

 region. Sexual differences occur in both species ; in R. temjjoraria 

 there is a large, black, glandular swelling on the inner side of the 

 hand of the male, and in R. esculenta the male has, at each angle 

 of the mouth, a loose fold of skin, the vocal sac, which can be 

 inflated from the mouth into a globular form. The skin is soft 

 and slimy owing to the secretion of mucous glands ; there is no 

 trace of exoskeleton. 



Endoskeleton. — The vcrtebrcd column (Fig. 922) is remark- 

 able for its extreme shortness ; it consists of only nine vertebne 

 (v. 1 — V. 9), the last followed by a slender, bony rod, the vrostyle 

 (u. sr). The second to the seventh vertebrae have similar char- 

 acters. The centrum (B, en) is somewhat depressed and has a 

 concave anterior and a ccmvex posterior face — a form known as 

 'proccelous. Each half of the nenrcd arch consists of two parts, a 

 pillar-like ijedielc ( jJf?) springing from the centrum and extending 

 vertically upwards, and a flat, nearly horizontal lamina {Im), 

 forming, with its fellow, the roof of the neural canal. When 

 the vertebras are in position, wide gaps -are left between successive 

 pedicles ; these are the intervertebral fwamina and serve for 

 the transmission of the spinal nerves. The zygapofliyscs {a. zyg) or 

 yoking processes are far better develoi^ed than in any Fish ; they 

 spring from the junction of pedicle and lamina, the anterior 

 zygapophysis having a distinct articular facet on its dorsal, the 

 posterior on its ventral surface. Thus when the vertebrae are in 

 position the posterior zygapophyses of each overlap the anterior 

 zygapophyses of its immediate successor. Laterally the neural 

 arch gives off on each side a large outstanding transverse process 

 (tr. i^r) ; its crown is produced into a very small and inconspicuous 

 neurcd sjnne (n. sp). 



The first or cervical vertebra (v. 1) has a very small centrum and 

 no transverse processes. There are no anterior zygapophyses, but 

 at the junction of centrum and arch there occurs on each side a 

 large oval concave facet for articulation with one of the condyles 



