270 Notices of Memoirs — Dr. P. L. Sclater — 



Physeteridge, Hijperoodon is confined to Arctatlantis, and, as already 

 explained, two very well-marked types of the Delphinidee, Delphin- 

 apterus and Monodon, are likewise exclusively denizens of the North 

 Atlantic ocean. Arctatlantis, therefore, may be said to be well 

 characterized by the possession of at least five genera of Marine 

 Mammals not found elsewhere, viz. Haliclioerus, Cystophora, 

 Hyperoodon, Delphinapterus, and Monodon. 



VII. The Middle Atlantic Sea-region, or Mesatlantis. — Mesatlantis 

 has certainly not so many forms of Marine Mammals confined to its 

 area as Arctatlantis, but there seem to be good grounds for its 

 separation. As we descend towards the tropics the true Seals 

 (Phocinse), which are constituted to live in colder water, gradually 

 fall off in numbei', and in Mesatlantis are no longer met with. But 

 in their place we find the genus Monachus or Monk-Seal restricted 

 to Mesatlantis, one species {M. albiventer) occurring in the Mediter- 

 ranean and on the North African coast, and a second (M. tropicalis) 

 being found in the West Indies. Mesatlantis is likewise the true 

 home of the well-marked Sirenian genus Manatus, one species of 

 which (M. Americaniis) frequents the coast of America and another 

 (M. Senegalensis) that of Africa. 



As regards the Cetaceans we are not able to say that Mesatlantis, 

 although well furnished with many generic types of this Order, has 

 anyone peculiar to it. We must therefore rest content with assigning 

 two genera of Marine Mammals,ilfonac/iMs and ilfana<Ms,as characteristic 

 forms or topomorphs of the Sea-Mammal life of Mesatlantis. 



VIII. The Indian Sea-region, or Indopelagia. — The Marine 

 Carnivora, so far as we know, are entirely foreign to Indopelagia, 

 but the Sirenians are well represented by the Dugong [Ralicore), 

 which pervades all its northern coasts from North Australia to India 

 and the Red Sea and down the African coast to Lamu.^ Whether 

 the species of Halicore found at different points within this area are 

 the same or diiferent, is still a matter of discussion, but there can be 

 no doubt that Halicore is an exclusive inhabitant of Indopelagia. As 

 regards the Whales of Indopelagia, we know that Physeter, Cogia, 

 and Ziphius, and numerous forms of Delphinidee occur there, but I am 

 not aware of any Cetacean that is entirely restricted to this Sea-region. 



IX. The North Pacific Sea-region, or Arctirenia. — As was pointed 

 out when speaking of Arctatlantis, Arctirenia has one genus of 

 Phocidaa (Phoca) in common with the North Atlantic, and three of 

 the species of this genus appear to be actually identical in these two 

 Sea-regions, whilst a fourth Phoca (P. fasciata) is only found in the 

 North Pacific. The Walrus [Trichechus) is again a form of Marine 

 Mammals common to both the great northern Sea-regions. But the 

 feature of Pinnipedian life that absolutely distinguishes Arctirenia 

 from Arctatlantis is the presence in the former of three (if not four) 

 well-marked species of the Eared Seals (Otariidte), which are 

 absolutely unknown in the vast extent of the Atlantic down at least 

 to 30° S. lat. 



^ A iine specimen of the Dugong from Lamn (on the east coast of Africa, lat. 

 2° 50' S.), obtained by Mr. J. C. Haggard in 1885, is in the British Museum. 



