246 BULLETIN 34, UNITED STATES NATIONAL 'MUSEUM. 



bones may be traced to a similar cause, esi)ecially the stress upon them 

 at the moment of starting a leap and alighting from it. The survival 

 of the elongate coracoid bone may be traced to use by pressure along 

 its longitudinal axis in the act of seizing the female, and possibly by 

 stress in the opposite direction when engaged in pushing objects out- 

 wards with the fore-feet, producing the effect of elongation. It is not 

 easy to assign a cause for the loss of the prtesternum and of various 

 cranial bones. It has been, perhaps, in these comparatively unused 

 parts that one effect of the general reduction in size and vigor which 

 has occurred during geological time since the Carboniferous and Trias- 

 sic periods, is to be seen. The loss of auditory organs is probably due 

 to disuse, the result of subterranean life.* 



The larval life of the Salientia has probably undergone important 

 modifications during the course of geologic time. The characters as- 

 sumed by tadpoles at different stages of their growth are not parallels 

 with known or probably to be discovered lower forms of life, but indi- 

 cate that the larva, like that of the Insecta, and like the mammalian 

 foetus, has had a developmental history of its own. In support of this 

 view I cite the anterior produition of the quadrate cartilage, which 

 carries with it the ceratohyal arch from its primitive attachment, and 

 the ultimate shortening of the same, and the return of the ceratohyal 

 to nearly its primitive connection with the skull. Further, the grad- 

 ual inclosure of the fore-leg in the external branchial chamber is to be 

 cited, the original position of the limb having been external. To these 

 may bo added the development of the epidermal stickers, of the labial 

 dermal comb, and of peculiar dermal glands in some tadpoles. None 

 of these peculiarities of larval life are found in the Urodela, and they 

 have been gradually assumed by the larviie of the Salientia in the course 

 of their existence, as though they were adult animals, and probably 

 in obedience to the same kind of laws. These are the interaction of 

 the animal and its environment. 



CLASSIEICATION. 



The natural divisions of the Salientia are the following : 



I. No tongue ; one pharyngeal opening of tLe Eustachian tube. 



Pterygoid bones inclosing Eustachian tubes below ; coracoids and procoracoids 

 divergent, connected by a cartilage which does not overlap that of the op- 

 posite side Aglossa. 



II. Tongue present ; two ostia pharyngea. 



Clavicle and coracoid of each side connected by a longitudinal arched carti- 

 lage, which overlaps that of the opposite side ; scaxjula free from the shull. 

 Arcifera. 



Clavicles and coracoids of both sides connected by a single narrow median car- 

 tilage ; scapula articulated with a special condyle of exoccipital. Grt.s/rec/(.m?Vf. 



Chvvicles and coracoids of both sides connected by a single median cartilage ; 

 scapula distinct from skull Firmisiernia. 



*See Facts and Opinions relating to the Deaf, by Alex. G. Bell, London, 1888, p. 89. 



