172 BULLETIN OF THE 



in a valuable paper entitled " On the Species of Manatee? (Manatus), and 

 on the Difficulty of distinguishing such Species by Osteological Characters,"* 

 states thai he finds the African and American species are distinguished by 

 only a single character, — the absence of the nasal bones in the African 

 species. Concerning the individual variation in the skulls of the two species, 

 lie oh crves as follows : " When Cuvier had a skull of the American and one 

 of the African Manatee, he gaveeighl characters by which the African skull 

 could be known from the American. Now we have a series of skulls of each 

 kind, we find that not one of these characters will separate the skulls of the 

 two countries from one another. Indeed, the skulls of each kind are so 

 variable that, after having them laid out before me for two or three days, 

 studying them every now and then, and inducing two proficients in the study 

 of bones, and in observing minute characters, to give me their assistance, we 

 came to the conclusion that we believed there was no character, common to 

 all the skulls of each kind, which could he used to separate them. As a 

 proof of the difficulty of so doing, I may state that there was one skull in the 

 series which had been long in the collection, and had been received without 

 any habitat, and neither of the three could decide to which of the series this 

 skull should he referred; and it was not until I accidentally observed the 

 character, derived from the absence of the nasal bones in the African kind, 

 that this question could be settled." 



Having myself been struck with the variability of osteological as well 

 as external characters in individuals of the same species, in both birds and 

 mammals, — a matter to which I have already often called attention, and the 

 consideration of which occupies a considerable portion of Part III of the 

 lire-cut paper, ■ — I can hardly refrain, in this connection, from citing further 

 the judicious remarks of Dr. Gray on this point. "The examination," he 

 savs, '• of a lame series of skulls of the hears (I'rsus) and Paradoxuri, shows 

 how difficult it is to distinguish species by the study of the >kulls alone. 

 Thus, when we have, a series of skulls of hears from different localities, which, 

 from their external form and habits, are known to be distinct species, it is 

 easy to shy which is the skull of U. thibetanus, U. syriacus, U. arctos, U. 

 us, and / '. ami ricanus, when we have the habitat marked on each ; but 

 the true test of the power of distinguishing the one from the other is to 

 determine to what species a skull belongs, of which we have no information 

 as to its origin ; and we have several skulls in the British Museum under 

 then- circumstances, and I cannot, with the best assistance at my command, 

 determine to which species they ought to be referred. And it is the same 

 with the Pciradoxuri." " If this is the case with the skulls," he continues, 

 " bow must the difficulty of distinguishing species with certainty be increased 

 when we have only fossil bones, which are generally more or less imperfect, 

 * Anc and Mag. Xat. Hist., 3d Ser., Vol. XV, pp. 130- 139, 1865. 



