9 6 Transactions. — Zoology. 



Mesojylodon layardl [ov, as I should call it, Dolichodon layardi) has a much 

 longer and more attenuated lower jaw, and much move slender teeth than 

 the Chatham Island specimen figured and described by Dr. Hector under 

 that name ; and T have very little doubt in my own mind that the Chatham 

 Island specimen will be found, when more perfect specimens are obtained, to 

 be the representative of a very distinct species of Dolichodon, which I would 

 propose provisionally to designate as Dolichodon traversii — a curious comment 

 on the comparative anatomists, who think that Dolichodon layardi of the Gape, 

 Callidon gilntheri of New South Wales, Petrorhynchus capensis of the Cape, 

 etc., etc., "all differ in so trifling a degree as not to exceed the range of 

 individual variations one often meets with in comparing a series of skulls of 

 the same species." Surely tlie author means domestic animals, and entirely 

 leaves out of the question the experience gained by the study of wild ones, and 

 the evidence afforded by the study of their geographical distribution. I must 

 think that when these authors become more exj^erienced they will wish their 

 observations to have a " tacit burial and oblivion," and perhaps, themselves 

 learn how to define genera and species. 



15. Berardiiis liectori. 

 I know notliing of this skull but from the figures and description of Dr. 

 Hector, and the skull has never been in England, so that I do not think 

 that any comparative anatomist has had the opportunity of seeing it. Dr. 

 Hector considered it the young of B. arnouxi. I at once saw that it was 

 different, but as it has the teeth in the front of the jaw, like Berardius, I 

 considered it best {and am still of the same opinion) to retain it in that genus, 

 with which it agrees in the position of its teeth as developed in the adult 

 aniiual, and in geographical distribution ; and your tracings of the ear-bones of 

 the two species show that there is a great affinity between them in the very 

 peculiar manner in which they are dotted. I consider the position of the teeth 

 a more important zoological chai-acter than a slight difference in the 

 "conformation of the naso-premaxillaiy region," a part that, as every zoologist 

 who has examined several skulls of different ages in the same species of Cetacea 

 knows, is very apt to vary ; but when a comparative anatomist di'aws his 

 conclusions from figures on the examination of a single specimen of a group, 

 he is often liable to be misled as to the value of the characters to which he 

 attaches much importance. Nothing showed this better than the published 

 results of the labours of a comparative anatomist, wlio has named, but not 

 defined, a multitude of species and genera from fragments of fossil Ijones, but 

 who, when he attempted to name recent skulls, as of crocodiles, of which he 

 has perfect S])ecimens under his eyes, named and described and puV^lished what 

 we now regard as three distinct sjjecies in one case, and two distinct species 

 in another, under the same name ; and, on the other hand, a series of skulls of 



