1863.] DR. J. E. GRAY ON THE CETACEANS. 197 



B. The front lobe of the sternum broad ; side curved outwards, with 

 a large pair of gular shields produced at the outer angles ; the 

 sides and the margin strongly dentated. Kinixys. 



1. Kinixys EROS A. The fifth vertebral plate rounded ; nuchal 

 none. 



2. Kinixys homeana. The fifth vertebral plate produced, an- 

 gular ; nuchal plate distinct. 



4. On THE Arrangement of the Cetaceans. 

 By Dr. John Edward Gray, F.R.S., etc. 



In the part of the ' Zoology of the Erebus and Terror' devoted to 

 the Cetacea I collected together all the materials within ray reach, and 

 published an arrangement of the genera, and notes on all the species, 

 of these animals which were then known to me, either from the 

 examination of the specimens in different museums, or from the de- 

 scriptions and observations in various zoological and whaling works. 

 The first part of the ' Catalogue of the Specimens of Mammalia in 

 the Collection of the British Museum,' which is devoted to the 

 Cetacea (published in 1850), may be considered as a revision of the 

 former essay, with the additional material that I had been able to 

 collect since it had been penned. During the thirteen years that 

 have elapsed since the publication of the Catalogue I have not 

 allowed any opportunity to escape of examining and comparing the 

 different specimens which have come under my observation, and I 

 have read with care all the papers and works that 1 have been able 

 to meet with bearing in any way on Whales and their allies. I am 

 now induced to lay the results, as far as the general arrangement of 

 the order is concerned, before the Society. 



Some zoologists pay little regard to such re-arrangements of genera 

 and the division of them into groups ; but this arises from the points 

 of view from which they regard them. If they look on them as 

 only artificial keys to discover the name of a genus, and thus arrive 

 at the name of a species, and if that is the object of the person who 

 forms them, then they are perhaps estimated at their right value. 

 But I have laboured at these and other arrangements which I have 

 suggested with a very different view. If it is considered desirable 

 to place the species in natural groups called genera, it is certainly 

 equally desirable that the genera so formed should be disposed in 

 the larger and larger groups in such an order as appears to the writer 

 most distinctly to exhibit the natural relations which the genera bear 

 to each other. If they are so disposed, then the name that is given 

 to a group of species is of little importance, as to whether the group 

 is called a genus or subgenus, a genus or subfamily, or a family. 

 They may be so regarded at the caprice or theory of the student, as, 

 whatever may be their nominal value, they are intended to represent 

 a natural group of species, arranged together so as best to represent, 

 according to the writer's view, the natural relation of the species 

 to each other. 



