REPTILIA. 



271 



bones, the larger of which (c) supports the 

 metatarsals of the fourth and fifth toes, 

 whilst the smaller (d) is situated between 

 the preceding and the metatarsal bones of the 

 second and third toes. This latter is also 

 slightly connected with the astragalus, which 

 alone supports the metatarsal bone of the 

 internal or representative of the great toe. 



The four first metatarsal bones are slender 

 and nearly straight, becoming progressively 

 longer as far as the fourth. The fifth is 

 short, wide, and curved superiorly towards 

 the larger of the two bones of the second 

 row (c), to the side of which it is articulated. 



The thumb or internal toe consists of two 

 phalanges, the second of three, the third of 

 four, and the fourth of five ; this is the 

 longest toe in the foot of a lizard, giving to it 

 the peculiar elongated and unequal form by 

 which it is immediately distinguished. The 

 fifth toe, although almost as short as the first, 

 is composed of four phalanges. 



The ungueal phalanges of all the toes are . 

 sharp, hooked, and pointed. 



The above description, with slight dif- 

 ferences as to the proportions, is applicable to 

 all those subgenera of lizards which have 

 their limbs fully developed, with the exception 

 of the Chameleons and certain Geckos. 



Even in the chameleon it is the proportions 



Fig. 188. 



Anterior Extremity of the Chameleon. 



of the carpal and tarsal bones that differ, 

 rather than their number or arrangement. 

 The five bones of the last row of the tarsus 

 are very large and oblong, instead of being 

 flattened. In the state of pronation and 

 torsion in which the foot is placed, the os pi- 

 siforme is attached to the inner margin ofthe 

 ulna, between it and the radius. The ulnar 

 carpal bone (fig 188, d) and the radial (c) are 



small, the central bone (e) being the largest of 

 all, and around this the five carpal bones of 

 the last row are arranged like the spokes of a 

 wheel. These five bones are longer than in 

 ordinary lizards, and in fact represent the 

 metacarpal bones as well as the last row of 

 the carpus, leaving the fingers possessed of 

 their proper number of phalanges. This re- 

 markable arrangement permits the foot of the 

 chameleon to be, as it were, split into two 

 divisions. The thumb, the index, and the 

 middle finger are connected by the skin into 

 one group, which is turned inwards, while the 

 two remaining fingers, similarly encased, are 

 turned outwards, thus enabling this remark- 

 able reptile to grasp firmly the boughs among 

 which it lives by a mechanism very similar to 

 that ofthe foot of a parrot or other scansorial 

 bird. 



In the tarsus of the chameleon the me- 

 chanism is very similar. The tibial tarsal bone 

 (Jig. 189, of.} and the fibular tarsal bone (b'} 



Fig. 189. 



Posterior Extremity ofthe Chameleon. 



are equally of small dimensions, whilst the 

 central bone of the tarsus (d), which articu- 

 lates with both the above, is of a spherical 

 form, and serves as a pivot for the move- 

 ments of the foot. It has another bone (c) 

 attached to its outer side, and the rest of its 

 circumference is occupied by the attachments 

 of the five metatarsal bones, the shape of 

 which resembles precisely that of the cor- 

 responding bones in the hand; and in like 

 manner they most probably represent the last 

 row of the tarsal bones of ordinary lizards 

 conjoined with those of the metatarsus. 

 This being allowed to be the case, the thumb- 

 finger of the chameleon consists of two pha- 

 langes, the first finger of three, the second 



