ON THE ARRANGEMENT OF THE MAMMALIA. 



191 



while, again, the Crustacea rise higher than the lower Mollusca. Hence 

 it would appear, that Nature rather presents us with a system of groups, 

 the lower rising above the termination of the upper, than with a series of 

 consecutive links, in which the last form of one group blends into the first 

 form of the next ; and hence, moreover, arises one of the difficulties attend- 

 ing a linear arrangement of the whole, or of parts, of the animal creation. 

 With respect to the arrangement of the Mammalia, in the Catalogue of the 

 Mam. Zool. Soc., it is to be observed, that the Insectivora are there 

 placed as a tribe, or great section, of the Carnivora. M. Blainville appears 

 correct in considering them as strictly entitled to rank as an order per 

 se ; and this is now the opinion of the author of the catalogue in question. 

 A second alteration of the arrangement in that catalogue, consists in the 

 collocation of the " Cetaces Herbivores" of Cuvier (the Duyong, the La- 

 mantin, &c.), with the Pachydermata, of which they are the aquatic form ; 

 having no affinity to the true Cetacea, beyond that of being, like them, 

 adapted for the element which they are destined to inhabit. 



In his views respecting the situation of the " Cetaces Herbivores," the 

 author accords with Professor Owen, to whom, he believes, is due the 

 merit of having first pointed out their true station. 



The arrangement of the class Mammalia, then, will stand as follows : 



SUB-CLASS. 



I^Placentalia. 



MAMMALIA. 



ORDER. 



1. Bimana. 



2. Quadrumana. 



3. Cheiroptera. 



4. Carnivora. 



5. Insectivora. 



6. Cetacea. 



7. Pachydermata (proper). 

 (aquatic). 



8. Ruminantia. 



9. Rodentia. 

 O. Edentata. 



l^Marsupialia. 11. Marsupialia. 



Teeth simple. 



Teeth compound. 



Teeth variable. 



Though the marsupials are here placed as an order, the author inclines 

 to the views of Cuvier, that this order ought to be regarded as a sub-class, 

 parallel to that of the placental Mammalia, and in such a light it will be 

 treated ; observations upon it being reserved for appropriate occasions. 



As the situation assigned to the Rodentia, below that of the Pachyder- 

 mata and Ruminantia, may, by some naturalists, be deemed a startling 

 innovation, the motives by which this arrangement has been influenced 

 may require explanation. 



The comparative anatomist will bear out the idea, that the structural 

 organization of the rodents is at a low ratio : this organic deterioration 



