146 REPTILIA. 



in several species small osseous rudiments of feet. The structure 

 of the posterior extremities in Pseudopus, Anguis, and Acontias, is 

 very interesting, as exhibiting an advanced condition, for here. in- 

 deed the single elongated pelvic bones are attached by ligament to 

 the transverse processes of the last dorsal vertebra ; in Eryx, Boa, 

 Typhlops, Amphisboena, &c., a pair of very elongated bones, con- 

 sisting occasionally of several pieces, lie always free, and at a dis- 

 tance from the vertebral column, in a parallel position with the rectum. 

 The Amphisbcenas, such as Trogonophis, exhibit the simplest form 

 of pelvis, since it consists in them of a very small flattened bone, 

 lying posteriorly beneath the integument, and near to the vertebral 

 column ; it may be regarded as a rudiment of the ilium. This struc- 

 ture is rather more complete in Ophisaurus. 



The Femur is of large size, and strongly curved in the Chelonia ; 

 the tibia and fibula are generally met with, with the exception of 

 the Anourous Batrachia, where only a single bone is found, as in 

 the fore-arm, presenting marks of division. There is frequently 

 developed in the extensor tendon of the femoral muscles, in many 

 Sauria, a patella, and in several Batrachia, as in Pipa, a second 

 patella occurs, situated behind, between the tibia and tarsal bones. 

 These last, disposed in three rows, continue partly cartilaginous 

 in the Tailed Batrachia, and present themselves under similar con- 

 ditions in the Ichthyic Reptiles ; on the contrary in the Anourous 

 Batrachia the two tarsal bones, corresponding to the os calcis and 

 astragalus, are constructed after the type of the crural bones, being 

 of an elongated form, while in front of them is situated a row of 

 lesser tarsal ossicles ; in the Chelonia, and Sauria, the small tarsal 

 bones are disposed in two rows. The metatarsal bones correspond 

 completely in the several orders with the metacarpals. The num- 

 ber and form also of the phalanges of the toes correspond, with 

 some exception, to those of the fingers. The last toe but one is 

 usually the longest. Several Ophidia, and Apodal Sauria, possess 

 the rudiment of a single toe, which is even provided with a nail, 

 as in Pseudopus, where the rudiment is very small, and turned in the 

 direction upward. It is more developed in the true Serpents, but it 

 is only in some genera, as Tortrix, Boa, Python, and also Eryx, in 

 which this rudiment of a toe supports a strong pointed claw. The 

 poisonous Snakes, Natterers, &c., appear to be destitute of these 

 structures. In Siren, and Coscilia, all trace of posterior extremities 

 is likewise wanting, 



