I20 RELATIONSHIP OF CETACEA 



of this group. A short rfeumd of what is at present thought 

 of the systematic position of this anomalous order is appro- 

 priate here. Alln-eclit went so far as to regard the Cetacea as 

 the nearest group of animals to the hypothetical Promammalia.i 

 But discounting liis arguments hy the removal of such of them 

 as relate to structure plainly altered by the singular mode of 

 life of these creatures, there is really a great deal to be said in 

 favour of his view. 



The chief facts which argue a primitive position among 

 mammals for the Cetacea are perhaps : (1) the slight union of 

 the rami of the lower jaw ; (2) the occasionally rather marked 

 traces of the double constitution of the sternum ; (3) the long 

 and simple lungs ; (4) the retention of the testes within the 

 body-cavity ; (5) the occasional presence (in Balaenoptera) of a 

 separate supra-angular bone. These points, however, are but few, 

 and are not of such great weight as those which ought to be pre- 

 sent to establish a claim to separate treatment for the Cetacea 

 as opposed to the Eutheria. If this group of mammals can be 

 tacked on anywhere, it appears to us tliat the nearest relatives 

 are not, as is sometimes put forward, the Ungulata or the 

 Carnivora, but the Edentata. There are quite a number of 

 rather striking features in which a likeness is shown between 

 these apparently diverse orders of mammals. The chief ones 

 are these: (1) the existence of traces of a hard exoskeleton, of 

 which vestiges remain in the Porpoise ; (2) the doul^le articula- 

 tion of the rib of the Balaenopterids to the sternum, with which 

 compare the conditions obtaining in the Great Anteater ; (3) the 

 concrescence of some of the cervical vertebrae ; (4) the share 

 which the pterygoids may take in the formation of the hard 

 palate ; (5) the fact that in the Porpoise, at any rate, as in many 

 Edentates, the vena cava, instead of increasing in size as it 

 approaches the liver, diminishes. 



Another group which is perfectly isolated is that of the 

 Sirenia. The alliance ad^•ocated by some with the Cetacea, and 

 quite recently renewed by Professor Haeckel, is contradicted by so 

 many important features that it seems necessary to abandon it. 

 The recent discovery of a fossil Sirenian jaw by Dr. Lydekker witli 

 teeth highly suggestive of those of Artiodactyla, may prove a clue. 

 A third group which is so isolated as to have been placed in a 



' Anat. Aiiz. i. 1886, p. :Ju8 ; and see Weber, ibid. ii. 1887, p. 42. 



