Cope.] J-Jt) [March 18, 



cranon except in Chamoeleon. The ulna and radius have about an equal 

 share in the carpal articulation, sometimes the ulna a little the greater. 



The constitution of the carpus is very uniform in Lacertilia with devel- 

 oped anterior limbs, the principal diversity being displayed by the Cha- 

 majleonidse. In all, we have in the proximal row three distinct elements, 

 the radiale, intermedium and ulnare (= pisiforme), the latter mainly ex- 

 ternal to the ulna and directed posteriorly. Distal to the radiale and 

 intermedium, and between them and the carpalia of the second row, is a 

 single small centrale. There are five carpalia, each corresponding to a 

 metacarpal. I have failed to find in any of the genera at my disposal any 

 of the carpalia fused together or wanting. In Chamseleon, on the con- 

 trary, Cuvier has shown that there is no ulnare, and that the centrale and 

 carpalia are fused into a single round median piece, to which the meta- 

 carpals are articulated. In all the normal Lacertilia the tendons of the 

 flexors of the digits are combined on the palm, and the point of junction 

 is occupied by a large flat sesamoid bone. The number of phalanges is 

 also remarkably uniform. They number in each digit, commencing with 

 the pollex, 2-3-4-5-3. The sole exception in the genera with well-de- 

 veloped extremities is Chamneleon. where the numbers are 2-3-4-4-3. 

 This genus difters also from other forms in the shapes of the metacarpals. 

 Normally they are cylindric and subparallel in position and united in a 

 common integument ; but in Champeleon they are flattened, with ex- 

 panded extremities, and divided into two bundles by a fissure, three 

 within and two without, enabling the three inner digits to oppose the two 

 outer round a branch of a tree. The number of digits in Lacertilia is 

 normally 5-5, but reductions take place presenting variations from 4-5 

 to 1-1, the posterior limb usually displaying a lesser degree of degener- 

 acy than the anterior, although not always. 



6. Posterior Limb. — The femur diff"ers from the humerus in having 

 a distinct head, which is marked off from a trochanter. The former is not 

 hemispherical as in Mammalia, but is somewhat compressed, and is oval 

 in section. The trochanter is on the inferior anterior side of the head, or 

 in the position of the little trochanter of the Mammalian femur. There is 

 no great trochanter, nor third trochanter. The condyles of the femur are not 

 as well defined as in the Mammalia, and the patellar groove is represented 

 by a shallow concavity without lateral ridges. Patella none, with some 

 exceptional rudiments, as in Varanus, e. g. In Chamseleo all the promi- 

 nent features of the femur are toned down ; the trochanter being repre- 

 sented by a ridge. The fibula is more slender than the tibia, and is larger 

 distally than proximally, the reverse of whit obtains in the tibia. The 

 latter has no crest. 



Like the carpus, the tarsus is very uniform in the Lacertilia, the sole 

 important modification being exhibited by the Chanueleonida?. There are 

 tvvo fused proximal elements, which are probably tibiale-intermedium and 

 fibulare. They are only distinct in Heloderma among North American 

 genera, but a trace of the suture is seen in Varanus. In most Lacertilia 



