LIMB-GIRDLES I 5 



cartilaginous sternum, which latter has no connection with the 

 ribs. The precoracoid is a large, ilat process, directed forwards, 

 not meeting- its fellow ; it is absent in Siren. 



The humerus articulates with both radius and ulna, and these 

 two bones of the forearm remain separate. The elements which 

 compose the wrist and hand exhil)it an almost ideally simple 

 arrangement, slightly varied by the frequent fusion of two or 

 more neighbouring carpalia into one, and by the reduction of the 

 number of lingers. Most frequently the intermedium and the 

 ulnar cai'pal element fuse together, and there is more often one 

 centrale instead of two. The wrist and hand of the Urodela 

 represent, however, no longer the entirely primitive pentadactyle 

 type, owing to the loss of one finger together with its metacarpal 

 and carpal element. Comparison with the Anura makes it 

 probable that the I^rodela have lost the pollex, their four fingers 

 being consequently the 2nd, 3rd, 4th, and 5th. Siren has four 

 or three fingers ; Proteus has only three fingers and three large 

 compound cai-^^al cartilages. In Amphiuma, with either three or 

 two fingers, the ulnare, intermedium, and carpale are fused 

 together, the radiale with the neighbouring carpale. The number 

 of phalanges in the four-fingered species is generally 2, 3, 3, 2 

 respectively. 



The pelvic girdle. — The ilium stands vertically to the vertebral 

 axis, slanting slightly forwards and downwards. It is attached 

 by means of a rib to only one vertebra, and this ilio-sacral 

 connection is acetabular in its position, i.e. it lies in the same 

 transverse plane with the acetabulum, in other words vertically 

 above it. The ventral portion of the pelvis is formed by one 

 large continuous mass, the united pubo-ischia, the anterior or 

 pubic portion of which extends forwards in the shape of a broad 

 triangle {Necturvs) or as a slender, stalked, Y-shaped cartilage, 

 the epipubis, which is often movably jointed at its base. The 

 lateral portion of the pubjc cartilage is always perforated by 

 the nervus obturatorius. Ossification is restricted to the ischium 

 and to the middle of the shaft of the ilium. The acetabular fossa 

 for the femur is closed. The tibia and fibula remain separate. 

 The foot is still more primitive than the anterior extremity, as 

 the majority of Urodela possess the full complement of five 

 toes, with 2, 2, 3, 3, 2 phalanges respectively. Concrescence of 

 the tarsalia applies most frequently to the fourtli and fifth distal 



