370 THE AMERICAN NATURALIST [Vol. XLII 



caudate forms as well as among the Miocene forms all of 

 the elements with the exception of the scapulae have be- 

 come cartilaginous, so that there remains in the modern 

 caudate amphibians only a bony scapula. This seems to 

 be the case in the Wealden Hyheobatrachus, but the single 

 specimen is not well enough preserved to furnish definite 

 information on this point. The pelvic girdle has, ap- 

 parently, undergone no change in the evolution of the 

 Caudata. The pubis is never ossified in either the 

 Branchiosauria or in the latter Caudata and the ischium 

 is usually plate-like, while the ilium is more or less 

 rounded. The sacral rib, of which there is never more 

 than one pair, is usually well developed. 



