ANATOMY 01' VERTEBRATES. 191 



intcrs})ace into the ' obturator foramina,' and becoming ossified in 



old IMonitors. The femur resembles that of 



the Crocodile, but with the imicr trochanter 



better developed, with a larger medullary cavity, 



and with a more marked depression on the outer 



condyle lor the fibidar articulation. The division 



ol' the back jiart of the head (jf the tibia is usually 



more marked. The head of the hbula, fig. 122, 



07, b, rises higher than in the Crocijdile. 



In Varmms niloticuis,^ the elongated iliac ['tiviBnf uiosinnitor 

 bone alnits against the transverse processes of 

 the two sacral vertebra, the first on the right side and the second 

 on the left side being applied on a plane higher than the 

 opposite processes : that of the first caudal vertebra also abuts 

 against the ilium on the left side. The ilium sends off a tuber- 

 osity in front of the sacro-iliac syndesmosis, and it joins the puljis 

 and ischium Ijy a broad suture. The trochanter arises from the 

 inner and back part of the proximal end f»f the shaft of the 

 femur. There are two ossified patelhc in the tendon of the great 

 extensor of the leg. The tarsus differs from that of the Crocodile 

 chiefly in there being a ' mesocnneifonn ' supporting the second 

 metatarsal, fig. 122, ii: but this is wanting in many lacertians. 

 The bone ci is as composite as in the crocodile. The fifth meta- 

 tarsal is flattened, and articulated farther Ijack than the rest, 

 extending along the outer side of the cuboid, c, to the calca- 

 neum, U: it supports an imguiculate toe of fjur phalanges, 

 fig. 122, 7 1 : the number of jihalanges in the other toes progres- 

 sively increases from two in the first, i, to five in the fourth, io, 

 with proportionate increase of length. 



The chief modification of the hiiid limb of Lacertians is fijund 

 in the Chameleon, fig. 123. The ilinm is a simple elongate, 

 subcomprcssed bo)ie descending vertically from the converging 

 ends of the sacral processes to the acetabulum. The fibula, 

 fio-. 123, b, 67, is bent outward. In the tarsus may be seen a 

 stunted homologue of the astragalo-uavicnlar bone, a', receiving 

 the end of the tibia ; and a larger calcaneum, b' , in like relation 

 with the fibula : these form a cavity for the spheroid ' cuneiform,' 

 d, by which the prehensile foot rotates on the leg ; and there is a 

 cuboid, c, exclusively supporting the fifth metatarsal, r. This 

 determination of the homologies of the tarsal bones with those of 

 the ambulatory lizards, shows the natiu-e of the five short but 

 metatarsially shaped bones supporting the toes, and settles the 



' xLiv. p. 149, No. 678. 



