AMPHIBIA. 399 



majority it has an ossified base bearing a cartilaginous expansion, and, as in 

 the Frog, is applied to the posterior edge of the united coracoids. It is 

 doubtfully homologous with the sternum of higher Vertebrata. 



The limbs with their respective girdles are absent in Gymnophiona, and 

 the Aistopoda among Stegocephali; the pelvic limb and girdle in Siren 

 lacertina among Ichthyoidea. The shoulder-girdle in Urodela has broad 

 scapular, coracoidal and large clavicular processes. The latter projects 

 somewhat forwards, and is free distally except in Menopoma, where it fuses 

 with the coracoid as in all Anura, inclosing a fenestra. Ossification takes 

 place in the glenoidal regions of both scapula and coracoid, and in the base 

 of the clavicular process. The amount of ossification varies, and is greatest 

 in the- Amir a. The clavicular ossification is in this order purely peri- 

 chondrial. Many of the Anura possess an anterior prolongation of the 

 interclavicular region (see pp. 81-2). The ventral ends of the coracoids 

 overlap in the Urodela and a few Anura, but in others of the last- 

 named order are connected by intervening interclavicular cartilage. Bony 

 scapulae, coracoids, and clavicles are found in most Stegocephali, but there 

 was evidently also a large amount of cartilage. 



Each half of the pelvis consists of a continuous cartilage in Urodela, 

 The ilium is partially ossified, as is the ischium, but the pubic region is 

 more or less permanently cartilaginous. In Salamandra perspicillata there 

 is, however, a continuously bony ischio-pubic region, and some Stegocephali 

 have well-formed and separate pubic and ischiadic bones. There is a 

 median ventral symphysis. The obturator nerve perforates the pubic 

 region, but neither in Urodela nor in other Amphibia does an obturator, i. e. 

 thyroid, foramen exist. The ilium of the Anura is of remarkable length, 

 inclined backwards, and the distal ends of the two ilia, together with the 

 ischo-pubic region, form a thin vertical plate. The acetabulum is a deep 

 depression in this plate. There is an ischium, but a pubic bone is 

 generally suppressed and its region ossified apparently by the ilium. It 

 has, however, been found in Dactylethra capensis, a Toad which also 

 possesses a simple epipubic cartilage. This cartilage, which projects 

 forwards medianly from the symphysis pubis, is absent in other Anura, but 

 large in Urodela, where it is Y-shaped. 



The limbs consist of the same parts as in higher Vertebrata. They are 

 relatively small as compared with the bulk of the body in the lower Urodela 

 and the Stegocephali, but are large and long, especially the hind extremities, 

 in Anura. The humerus, radius, and ulna are cylindrical bones with car- 

 tilaginous ends in Urodela, and the same is true of the corresponding sections 

 of the hind-limb. The cartilage contains much calcareous deposit in Anura, 

 in which also the radius is fused with the ulna, the tibia with the fibula. 

 The bones of the carpus and tarsus are usually cartilaginous in Urodela, 

 ossified in Anura. There are many differences observable in the carpal and 



