REPTILIA. 



267 



and an acromion process that almost equals it 

 in size, is quite peculiar to the Chelonian rep- 



Fig. 178. 



Scapular Apparatus of Chelys. 

 a, scapula ; b, acromion process ; c, coracoid bone. 



tiles, nothing like it existing in any other ver- 

 tebrate animals : nevertheless, the relations of 

 these bones, and the muscles derived from 

 them, prove clearly enough their identity, and 

 allow of strict comparison with those of other 

 races of vertebrata. 



The pelvis is always composed of three 

 distinct bones on each side, which contribute, 

 as in quadrupeds, to the formation of the coty- 

 loid cavity, viz. the ilium (fig. 179, .), which is 



Fig. 179. 



Pelvis of the Turtle, 

 a, os ilii ; b, os pubis ; c, os ischii. 



of an elongated form, and attached by liga- 

 ments to the transverse processes of the 

 sacral vertebra, as well as to the neighbour- 

 ing part of the eighth pair of dilated ribs : 

 secondly, the pubis b, and the ischium c, both 

 of which, expanding as they descend towards 



the plastrum, terminate by joining their fellows 

 of the opposite side. 



The cylindrical bones of the extremities 

 resemble those of other four-footed reptiles, 

 and present no peculiarity worthy of special 

 notice, except in a geological point of view. 



In the turtles, all the bones of the carpus are 

 flattened, and of a squarish form. In the first 

 row there are two bones (fig. 180, c, d.} con- 

 Fig. 180. 



Anterior extremity of a Turtle. (After Cuvier.) 



nected with the ulna ; and in the second row 

 there are five smaller ones (1, 2, 3, 4, 5.), to 

 which are appended the five metacarpal bones. 

 In addition to the above, there is an interme- 

 diate bone (e), situated beneath the ulnar car- 

 pal bone (c), and above the second and third 

 bones of the last row, (2, 3.) This piece, 

 Cuvier thinks, corresponds with the dismerr- 

 bered portion of the trapezoid bone, met with 

 in monkeys. Lastly, there is a great crescent- 

 shaped bone (/), which is adherent to the 

 ulnar margin of the piece which supports the 

 metacarpal bone of the little finger ; this is the 

 os pisiforme, although its situation is so low 

 down. 



Between the bone (1), which supports the 

 metacarpal bone of the thumb, and the ra- 

 dius (a), the connexion during a long period 

 is effected entirely by ligaments, without any 

 appearance of the great scaphoido-semilunar 

 bone which exists in the other sub-genera, 

 but with age a small ossicle makes its appear- 

 ance in this situation. In very large indivi- 

 duals, the two antepenultimate bones of the 

 second row are consolidated into one. 



The metacarpal bone of the thumb is 



