264 PROOEEDINOS OF THE ACADEMY OP 



and especially such non-adaptive characters as the union of the 

 scaphoid and lunar bones, indicate their community of origin, 

 and point to the derivation of Pinnipcdias from a specialized car- 

 nivorous stock. The tendencies of the specialization in the Pin- 

 nipedia, as the great reduction iu size of the milk teeth, the 

 decreasing differentiation of the other teeth, and the modifications 

 of the form, are towards the Cete ; the extinct Zeuglodonts, and 

 especially the Basilosauridae, even indicate the possibility, if not 

 probability, of the derivation of the Cete from a Pinniped avus. 

 At the most, however, it can onl}- be claimed that no quadrupedal 

 t3^pe now exists, or has left its remains, so far as is 3'et known, 

 which so nearly fulfils the conditions of intervention between 

 ordinary quadrupeds and mutilates as the Pinnipedia. It is 

 possible, however, that the resemblances in question may be 

 adaptive, and it must not be forgotten that similar tendencies, 

 but in a very minor degree, are exhibited by a specialized lutrine 

 type (Enh3-dris, or sea otter). A careful comparative study of 

 the detailed anatomy, and especiall}' of the brain, in the general- 

 ized Educabilia,* and the Pinnipeds, Sirenians, and Cetaceans 

 might go far to dissipate the doubts now involving the question, 

 and determine the truth one way or another. 



It appears, however, to be demonstrable, from what is already 

 known of the brain and the organization generally, that the muti- 

 lates are at least the oflfshoots from the same common progenitor 

 as the carnivores and other Educabilia ; and in view of the near 

 relations, even within the limits of the "super-order," it appears 

 also to be much more probable that the two orders of mutilates 

 have been derived from a common mutilate progenitor, than that 

 they have diverged independently from two different types of 

 quadrupeds within such circumscribed limits. Nor is there any 

 cogent evidence, apparently, against the descent of the Sirenians 

 from a mutilate descendant of a proto-inniped ancestor, either as to 

 adaptation for a vegetable regimen or dentition. 



The autlior has, therefore, felt obliged, after mature reflection, 

 to adopt the views, current among most of the special students of 

 the mammals, that the Cetaceans and Sirenians are orders more 

 nearly related to each other than is either to auy other order, and 



' The author has not access to the material, at present, for such an in- 

 vestigation. 



