1864.] DR. DAWSON ON CLASSIFICATION OF ANIMALS. 257 



eists of an assemblage of genera resembling each other in general 

 aspect. Most large orders are readily divisible into such assem- 

 blages, which, though in themselves somewhat vague, have the 

 advantage of being formed on grounds which, being conspicuous 

 and obvious at first sight, much aid the naturalist in the prelimi- 

 nary parts of his work. For example, among the carnivorous 

 mammalia such groups as the Mustelidce or weasels, the Canidce 

 or dogs, the Felidce or cats, are so obvious that any member of one 

 of these groups can be referred to that to which it belongs almost 

 at first sio-ht. Still I do not resfard families as necessary divi- 

 sions of the order. Some small orders may not admit of division 

 into families ; and even where such division is admissible, the 

 genera may be studied as members of the order, without being 

 grouped in families, though this grouping is often very useful and 

 convenient. 



It is important to observe, before leaving this part of the sub- 

 ject, that, in consequence of the great multiplication of species in 

 some groups, and the close scrutiny of their structures, it is the 

 tendency of specialists to form many small genera. This leads to 

 the construction of numerous families, many of which would more 

 properly remain as genera. A still worse consequence is, that, in- 

 stead of forming sub-orders and sub-classes, such specialists often 

 call sub-orders or even families orders, and raise sub-classes or 

 orders to the rank of nominal classes, thus introducins; a confusion 

 which leads the student to suppose that these terms have no defi- 

 nite meaning. I would further observe here, that I do not so 

 much insist on the use of one name for a group rather than another, 

 as on the constant use of each term for groups truly equivalent in 

 the system. 



It may be necessary here to state that the formation of orders 



on the ground of rank, and of families on the ground of general 



aspect, does not exclude the ideas of rank and general aspect from 



the province or class. On the contrary, as a secondary ground, 



general aspect is a good character in the province and class, and 



a gradation of rank can be perceived in provinces and classes. In 



the provinces, the Vertehrata stand highest, and the Rudiata 



lowest, the Artlculata and the Mollusca being nearly equal, and 



their lower members not so high as the highest Radiata ; so that 



they would stand in a diagram thus : 



Vertebrates 

 Articulates MoUusJcs 



Radiates. 

 Vol. I. R No. 4. 



