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ON THE DISTRIBUTION OF MARINE MAMMALIA.* 

 By P. L. Sclater, M.A., Ph.D., F.R S. 



I. Introductory Remarks, 



Most of the recent writers on Geographical Distribution have 

 confined their attention to terrestrial mammals, or at any rate 

 have but casually alluded to the marine groups of that Class. 

 On the present occasion I wish to call your attention to some of 

 the principal facts connected with the distribution over the 

 world's surface of the marine or aquatic members of the Class 

 of Mammals. 



Aquatic mammals which pass their lives entirely, or, for the 

 greater part, in the water are, of course, subject to very different 

 laws of distribution from those of the terrestrial forms. As 

 regards aquatic mammals, land is of course an impassable 

 barrier to their extension, and, subject to restrictions in certain 

 cases, water offers them a free passage. Just the opposite is the 

 case with the terrestrial mammals, to which in most cases land 

 offers a free passage, while seas and rivers restrain the extension 

 of their ranges. 



The groups of aquatic mammals that are represented on the 

 earth's surface at the present time are three in number, viz. : — 



(1) the suborder of the Carnivora, containing the Seals and their 

 allies, generally called the Pinnipedia, which are semi-aquatic ; 



(2) the Sirenia, which are mainly aquatic ; and (3) the Cetacea, 

 which never leave the water, and are wholly aquatic. We will 

 consider briefly the principal representatives of these three 

 groups, following nearly the arrangement of them employed in 

 Flower and Lydekker's * Mammals Living and Extinct.' 



II. Distribution of Pinnipeds. 

 The Pinnipeds, which I will take first, comprise three dis- 

 tinct families — the Otariidce, the Trichechida, and the Phocidce. 



* By the courtesy of Dr. Sclater we have received an advance proof of this 

 important paper, read before the Zoological Society of London on March 16th. 



