742 



SCIENCE. 



[N. S. Vol. V. No. 124. 



sage, while seas and rivers restrain the ex- 

 tension 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 representa- 

 tives 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 distinct families — the Ota- 

 riidse, the Trichechidse, and the Phocidse. 

 Beginning with the OtariidcB, or Eared Seals, 

 commonly known as Sea-lions and Sea- 

 bears, we find the greater number of the 

 species confined to the South Polar Ocean, 

 where they pass most of their time at sea, 

 but, as is well known, resort to the land at 

 certain seasons for breeding purposes. In the 

 Atlantic Ocean, so far as I know, the Eared 

 Seals have never been ascertained to occur 

 further north than the estuary of the La 

 Plata on the American coast and the vicinity 

 of the Cape on the African coast. But in 

 the Pacific, on the contrary, three distinct 

 species of Otaria are found all over the Arctic 

 portion of that ocean, and there are well 

 founded traditions of Eared Seals having 

 been formerly met with, in the Galapagos, 

 while they still occur on the coast of Peru 

 and Chili. I think, therefore, we may as- 

 sume that Otaria was originally an Anai'ctic 

 form, but has traveled northwards along the 

 west American coast and is now firmly 

 established in the N'orth Pacific. In a 

 parallel way in the class of birds, the Al- 

 batrosses (Diomedea) , which are essentially 



a group of the Antarctic Seas, are repre- 

 sented by three distinct species in the 

 North Pacific. 



The second family of the marine Car- 

 nivora, on the other hand, the "Walruses 

 {TrichechidoB) , are entirely Arctic in their 

 distribution ; one species ( Trichechits ros- 

 marus) being peculiar to the liorth Atlantic, 

 while a second nearly allied species (T. 

 obeaus) takes its place in the Northern 

 Pacific. 



The third family of Pinnipeds is more 

 numerous and varied, both in genera and 

 species, than the two preceding and has a 

 more extended range. The Seals, Phocidm^ 

 embracing about nine different generic 

 forms, are most numerous in the Arctic and 

 Antarctic seas, but are also feebly repre- 

 sented in some intermediate localities. Be- 

 ginning with the North Atlantic, we find 

 several species of Phoca inhabiting vari- 

 ous parts of this area, and the Gray 

 Seal (Salichcerus) and the Bladder-Seal 

 ( Cystophora) exclusively confined to it. In 

 the North Pacific all the four true Seals be- 

 long to the genus Phoca, and three of them 

 are identical with the North Atlantic spe- 

 cies, but when we descend as far south as 

 the Gulf of California on the American 

 coast we meet with a species of Sea-elephant 

 {Macrorhimis) which, like Otaria, has no 

 doubt penetrated up here thus far from its 

 ancestral abode in the Antarctic Ocean. 



Eeturning to the central Atlantic we 

 find two species of seals inhabiting these 

 waters, both belonging to the same genus 

 Monachus. One of these {M. alhiventer) in- 

 habits the Mediterranean and the adjoining 

 coasts of the Atlantic, while the other (M. 

 tropicalis) is in these days restricted to some 

 of the smaller and less known islands of the 

 West Indies. 



The Phocidce of the Antarctic Ocean all 

 belong to genera distinct from the Arctic 

 forms and more nearly allied to Monachus, 

 the seal of the mid- Atlantic. They are of 



