BATRACHIA. 



805 



pital condyle is obsolete, while there are two distinct ones in the Rhachitomi (Fig, 

 170). In the remaining orders the centrum of the vertebra is not segmented. The 

 Embolomeri differ remarkably from all other Vertebrata, in having between the centra 

 another set of vertebral bodies, so that each arch has two corresponding bodies. 

 In the Stegocephali the vertebrse are simple, and the temporal fossse are over-roofed 

 by bone arranged in distinct segments, as in the preceding orders (Figs. 170 and 172). 

 In the remaining orders, the temporal fossa is open 

 above. In the Proteida there is an epiotic bone, 

 which is unknown in the orders which follow. Like 

 the Urodela, it has a series of distinct caudal verte- 

 brae, and the bones of the front are not connate, and 

 the bones of the second segment of the limbs are 

 separate. The Urodela include the salamanders. 

 The Gymnophiona are limbless, and without scapular 

 and pelvic arches, and the tail is short or wanting. It 

 includes the worm-like Cfeciliidse. The Anura, or 

 frogs and toads, have various peculiarities of struc- 

 ture. The bones of the second segment of the arm 

 and leg are co-ossified, as are the bones of the roof 

 of the brain case. The caudal vertebrae are repre 

 sented by a style or rod of bone.. 



The genera of Stegocephali present us with :i 

 variety of external forms, similar to those know: i 

 among the Reptilia ; thus Sauropleura resembles a 

 long-limbed lizard, and Tuditanns a short-limbed 

 one ; Amphibamus, found in the Illinois coal-field, i» 

 a still more stout and squat form. In Ptyonius and 

 Oestocephalus we have very elongate types, but in 

 Phlegethontia, and probably Molgophis, we havr 

 veritable Batrachian snakes, the Phlegethontia 

 linearis resembling a whip-snake in its proportions. 

 In some of the Labyrinthodonts of the Old World we see forms rivalling the Sau- 

 rians in power of armature and protective shields. 



Fig. 172. — Skull of Cricoius crassidiscus. 



Order V. — PROTEIDA. 



This order embraces but one recent family, the Peoteid^, which includes but two 

 genera of existing species, Proteus and JVecturus. The former is represented by two 

 or three species which live in the waters of the caves of Carinthia and Dalmatia in 

 Austria. These animals have persistent external gills, and four legs, each of which 

 supports but three toes in front and four behind. The powers of vision of the species 

 are imperfect, and their colors are pale, as in other cave animals. Proteus anguinus 

 is the typical species. In the genus Nectiirus there are four toes on all the feet. The 

 lai-val gills are persistent in this genus also. There are two species, JST. maculatus, of 

 the rivers and lakes of the upper Mississippi and great lakes system, and JV. punctatus, 

 from the coast rivers of the Carolinas and Georgia. The color pigment is well devel- 



VOL. III. — 20 



