1914] Taylor: Aquatic Adaptation in the Carnivora 



495 



there are illustrated several stages in the adaptive process, rang- 

 ing from the less specialized genera Phalaradon and Mixosaurus 

 to the more specialized Cynibospondylus and the most specialized 

 Baptanodon. Thus we are able to contemplate a series of begin- 

 ning stages of aquatic adaptation, in a terrestrial to littoral- 

 marine group, on the one hand, and a series of advanced stages 

 in a group exclusively marine, on the other. Although the gap 

 which intervenes is considerable, the pinnipedian carnivore Phoca 

 exemplifies a stage of adaptation probably somewhere between the 

 two series, and as palaeontological exploration is carried forward 

 it is not unlikely that more intermediate stages will be discovered. 



SUMMAEY 



The following points covered in this paper may be broadly re- 

 capitulated : 



1. The detailed consideration of the osteology of Latax and 

 Lutra emphasizes, first, the close relationship of the two, in that 

 both are fundamentally alike, having probably descended from 

 a common ancestral form ; and second, the fact of the divergence 

 of the former from the latter, the bulk of the modifications in 

 skeletal structure being clearly and intimately related to adapta- 

 tion to life in the water. 



2. The facts pertinent to the palaeontologic history of Latax 

 indicate its descent from a lutrine ancestor, probably near the 

 genus Lutra. 



3. The consideration of this concrete case of a species appar- 

 ently in a stage of evolution transitional between a form of ter- 

 restrial and one of marine habit cannot be shown to favor one of 

 the proposed methods of evolution to the exclusion of others. 



4. This study suggests a most significant possibility, namely 

 that in mammals, during the transition between a land and water 

 habitat, a crushing type of dentition is likely to be foiind. A 

 broad dentition, fitted only for crushing, may, in other words, 

 be intermediate between the more compressed and acutely tuber- 

 culated cheek-teeth of land-dwelling forms in which a dental 

 armature fitted for cutting and tearing is a necessity, and the 

 more nearly isodont cheek-teeth of marine-dwelling forms in 

 which the dentition serves no other function than that of catch- 

 ing and holding. 



