ANATOMY OF VERTEBRATES. 191 



interspace into the ( obturator foramina,' and becoming ossified in 



old Monitors. The femur resembles that of 



the Crocodile, but with the inner trochanter 



better developed, with a larger medullary cavity, 



and with a more marked depression on the outer 



condyle for the fibular articulation. The division 



of the back part of the head of the tibia is usually 



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



67, b, rises higher than in the Crocodile. 



In Varanus niloticus, 1 the elongated iliac Feu-is of the Monitor 

 bone abuts against the transverse processes of 

 the two sacral vertebrae, 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 pubis 

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

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

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

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

 chiefly in there being a ' mesocuneiform ' supporting the second 

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

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

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

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

 neum, l)\ it supports an unguiculate toe of four phalanges, 

 fig. 122, v : the number of phalanges in the other toes progres- 

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

 with proportionate increase of length. 



The chief modification of the hind limb of Lacertians is found 

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

 subcompressed bone descending vertically from the converging 

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

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

 stunted homologue of the astragalo-navicular bone, of, receiving 

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

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

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

 cuboid, c 3 exclusively supporting the fifth metatarsal, v. This 

 determination of the homologies of the tarsal bones with those of 

 the ambulatory lizards, shows the nature of the five short but 

 metatarsially shaped bones supporting the toes, and settles the 



1 XLIT. p. 149, No. 678, 



