414 



Vertebrata. 



fingers is usually five, but may be smaller ; the phalanges vary in 

 number ; in the Lizards they are generally as follows : two in the 

 thumb, three in the second, four in the third, five in the fourth, 

 three in the fifth digit. 



Pig. 340. 



Mg. 341. 



Fig. 342. 



rig. 340. Carpus of a Turtle. IT lower portion of the ulna, B of the radius, 

 u ulnare, i intermedinin, r radiale, c oentrale, 1 — 5 carpals first to fifth ; s pisiform : I — V 

 metacarpals. — After Gegenbaur. 



Fig. 341. — Carpus of a Lizard {Lacerta agiUs). — Modified from Gegenbaur. 



Fig. 342. — Left half of pelvis of a Lizard (Varanus). Jl Ilium, a its hind end, 

 Js ischium', P pubis, I acetabulum. — After Gegenbaur. 



The pelvis is composed of three bones on each side, the ventral 

 portion being separated by a large fenestra into anterior and posterior 

 parts, which ossify separately, the pubis and the ischium; 

 they are connected medianly with their fellows of the other side; all 

 three bones generally take part in the formation of the acetabulum. 

 A pelvis is usually altogether absent from the Ophidia, but occasion- 

 ally rudiments of it are present, e.g., in the Peropoda with rudimentary 

 hind limbs. In the tarsus* some of the bones are always fused ; 

 it is important to note, that the proximal row of tarsals with which the 

 centrale is also counected, is usually closely united with the distal end 

 of the leg, and movement in the ankle occurs between the proximal 

 and distal rows of tarsals, whilst there is very little or none between 

 the leg and the proximal row {cf. Mammalia) .f The toes are like 

 the fingers ; five are usually present ; the number of joints varies : in 

 Lizards beginning with the hallux, as a rule, two, three, four, five, 

 four. 



The brain of Reptilia is generally rather small. In some forms, 

 especially in Crocodiles, the cerebrum attains relatively large 



" In Crooodilia the pubis is, however, excluded from the aoetabuliun, which is 

 formed by ilia and ischia alone. 



t As regards special arrangements it may be mentioned that the bone of the 

 proximal row, which corresponds with the oalcaneiun of Mammalia, is provided in the 

 •Crocodilia with a similar process (tuher calcis). 



