HIND-LIMB. 1 39 



The following muscles should be noticed : Pubo-ischio- 

 tibialis, a large powerful muscle probably answering to the 

 mammalian gracilis ; it is absent in Chelonians, Crocodiles, 

 and Birds. The pubi-tibialis, a double muscle, though 

 single in many Lizards ; it is absent in the Crocodile. 

 The two peronei are separate ; in many Lizards they form 

 a single mass. The inner head of the gastrocnemius is 

 tibial in origin and double. 0. C. 64 Y v. 



C. 178. Left hind-limb of a Lizard (Varanus salvator), showing 

 the deep muscles. The connection between the flexor 

 tibialis externus and internus and the second part of the 

 inner head of the gastrocnemius should be noted ; also 

 a curious long slender tendon rising from the lower 

 margin of the caudi-femoralis and inserted upon the 

 tibia in conjunction with the pubi-tibialis. 0. C. 64 Y w. 

 Gadow, Morph. Jahrb., Bd. vii. 1882, p. 329. 



C. 179. Left hind-limb of a Crocodile (Crocodilus acutus), 

 showing the nerves and superficial muscles. Several that 

 in the Monitor are single are here replaced by two, for 

 instance ilio-tibularis, caudi-femoralis, ambiens. Several 

 also are entirely absent, notably the large pubi-ischio- 

 tibialis. The first part of the ambiens is strikingly bird-like; 

 its tendon passes diagonally outwards over the knee and 

 is inserted into the peroneus posterior. More or less 

 intimate connections occur between the superficial muscles 

 in the region of the ankle; thus, the tibialis anticus joins 

 the extensor longus digitorum, and the peronei unite with 

 one another and with the gastrocnemius. The great size 

 of the caudi-femoralis indicates its importance. It seems 

 to act not only as a retractor of the whole limb, but also to 

 produce the lateral movements of the tail. 0. C. 63 G. 



C. 180. Nervesand deep muscles of the right hind-limb of a Croco- 

 dile ( Crocodilus acutus] . The flexor tibialis internus is more 

 complex than in the Monitor : two of its divisions unite in 

 a common tendon with the flexor tibiylis externus. The 

 tendon is forked and inserted by one end upon the neck of 

 the tibia, and by the other, which runs down the leg parallel 



