H LlAIli-GlRDLES 15 



cartilaginous sternuiu, which latter has no connection with the 

 ribs. The precoracoid is ;i large, flat process, directed forwards, 

 not meeting its fellt)w ; it is absent in Siren. 



The humerus articulates with both radius and ulna, and these 

 two bones of the forearm remain separate. The elements whicji 

 compose the wrist and hand exliibit an almost ideally simple 

 arrangement, slightly varied hy the frequent fusion of two or 

 more neighbouring car])alia into one, and by the reduction of the 

 number of tingers. Most frequently the intermedium and tlie 

 ulnar carpal element fuse together, and there is more often one 

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

 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 Urodela have lost the pollex, their four fingers 

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

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

 compound cari.)al cartilages. In Amiihiuma, with either three or 

 two fingers, the ulnare, intermedium, and carpalc 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 verticall\- 

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

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

 ])ubic portion of which extends forwards in the shape of a broad 

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

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

 lateral portion of the pubic cartilage is always perforated l)y 

 the nervus obturatorius. Ossification is restricted to the ischium 

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

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

 The foot is still more primitive than tlie 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 fourth and liftli distal 



