144 REPTILIA. 



clavicular bone, forming, with the preceding, the articulating cavity 

 for the humerus ; the two clavicles rest upon the supra-lateral bor- 

 der of the broad sternum. The structure is in a like degree simple 

 in Chameleon, and also in Chirotes. In Anguis and Pseudopus 

 there is found beneath the skin a bony girdle, without any further 

 development of extremities ; in this the anterior flattened clavicles 

 which converge and come in contact with each other, are distinct, 

 and in a less degree, may the rudimentary scapula, and still less the 

 posterior clavicle, be distinguished. In Amphisboena, at least in 

 Trogonophis Wiegmanni, only a rudiment of the anterior clavicle 

 is present, so that this animal exhibits the greatest amount of im- 

 perfection, and, as it were, the last link in the interesting metamor- 

 phoses of the anterior extremities in the Sauria. While, however, 

 these subcutaneous rudiments of bones occur in the serpent-like 

 Sauria, it would appear, at least according to present researches, 

 that in the Ophidia every trace of anterior extremities has disap- 

 peared. In the Tailed Batrachia, as the Salamanders and Tritons, 

 the structure is more simple. The scapulae continue in a more 

 cartilaginous condition, and instead of the clavicles, there is found 

 anteriorly, a broad, partly cartilaginous plate, which comes in con- 

 tact with that of the opposite side. The structure of these parts is 

 similar in the Icthyic Reptilia ; in Siren, and Proteus, the scapula is 

 at least osseous inferiorly, but in Amphiuma is reduced to a mere 

 cartilaginous plate. Every trace of extremities appears to be want- 

 ing in Cecilia. 



In the disposition of their Anterior Extremities, the Reptilia ap- 

 proximate the Mammalia. The humerus is of moderate length, and 

 in the Chelonia very much bent, and twisted in such a manner in 

 relation to the axilla, that the arched surface looks in the direction 

 backward j two bones are generally met with in the fore-arm, whereof 

 the radius is usually placed anteriorly, but in the Chelonia, inter- 

 nally and posteriorly ; it is only the Tailless Batrachia who have 

 a single bone to their fore-arm, but even this presents a double 

 groove indicative of its division into two bones, and possesses inter- 

 nally a double medullary canal. In many Reptiles a peculiar ossicle 

 is developed in the extensor tendon of the humerus, above the pro- 

 jection of the olecranon, and, from its resemblance to the patella, has 

 been called the patella brachialis. It occurs in many Batrachia and 

 Sauria, more rarely in the Tortoises, but is wanting in many genera, 

 and in the Crocodiles. In all Reptiles, the carpus is composed of 

 a double, more rarely a single or triple, series of small ossicles, which 



