ZO RELATIONSHIP OF CETACEA CHAP. 
of this group. <A short résumé of what is at present thought 
of the systematic position of this anomalous order is appro- 
priate here. Albrecht went so far as to regard the Cetacea as 
the nearest group of animals to the hypothetical Promammalia.? 
But discounting his arguments by 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 that 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 double 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 
Kdentates, 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 advocated 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 with 
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 
1 Anat. Anz. i. 1886, p. 338 ; and see Weber, ibid. ii. 1887, p. 42. 
