658 



PHYLUM CHORDATA : CLASS AMPHIBIA 



widely separated raedianly, and connected by a large arched epicoracoid, 

 overlapping its fellow. 



The skeleton of the fore-Umb consists of an upper arm 

 or humerus, a fore-arm in which the inner radius and the 

 outer ulna are fused, a wrist or carpus including two 

 proximal and three distal elements, and a central piece 



Fig. 379. — Brain of frog. — After Wiedersheim. 



I. Dorsal Aspect. — o.L, Olfactory lobes ; c.h., cerebral hemi- 

 spheres ; P., pineal body, rising from region of optic thalami ; 

 op.L, optic lobes ; cb., rudimentary cerebellum ; M.O., medulla 

 oblongata. 

 II. Ventral Aspect. — The numbers indicate the origms of the 

 nerves, ch., Optic chiasma ; T.c, tuber cinereum (infundib- 

 uluni) ; //., hypophysis. 

 III. Horizontal Section. — l.v., 1 and 2, lateral ventricles of cerebrum ; 

 P.m., foramen of Monro ; V., 3 and 4, third and fourth ven- 

 tricles ; Aq., cavities of optic lobes and aqueduct of Sylvius 

 from third to fourth ventricle. 



wedged in between them, five metacarpal bones, of which 

 the first — corresponding to the absent thumb — is very 

 small, and four fingers, of which the two innermost have 

 two joints or phalanges, while the two others have 

 three. 



The pelvic girdle is shaped like a V, or like a pair of 

 tongs. The ends are cartilaginous and articulate with the 



