746 



SCmNGE. 



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



Sirenians are well represented by the Du- 

 gong (Halicore), -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 different is still a 

 matter of discussion, but there can be no 

 doubt that Halicore is an exclusive inhabi- 

 tant of Indopelagia. As regards the Whales 

 of Indopelagia, we know that Physeter, 

 Cogia and Ziphius, and numerous forms of 

 DelphinidcB, occur there, but I am not aware 

 of any Cetacean that is entirely restricted 

 to this Sea-region. 



IX. THE NORTH PACIFIC SEA-EEGION, OR 

 ARCTIRENIA. 



As was pointed out when speaking of 

 Arctatlantis, Arctirenia has one genus of 

 PhocidcB (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 Pa- 

 cific. The Walrus (Trichechiis) 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 foi'mer of three (if not 

 four) well-marked species of the Eared 

 Seals (Otariidce), which are absolutely un- 

 known in the vast extent of the Atlantic 

 down at least to 30° S. lat. 



Arctirenia has unfortunately lost its Sire- 

 nian, Steller's Sea-Cow (Ehytina stelleri), 

 the largest and finest modern representative 

 of this formerly prevalent group, which since 

 the days of the Pleistocene, has greatly di- 

 minished in numbers, but I think we may 

 still treat Rhytlna as one of the characteris- 

 tic forms of the Arctirenian Sea-region. 

 The North Pacific is also even at the pres- 



* A fine specimen of the Dugong from Lamu ( on 

 the east coast of Africa, lat. 2° 50' S. ), obtained by 

 Mr. J. C. Haggard in 1885, is in the British Museum. 



ent day the sole possessor of a remarkable 

 genus of Whalebone Wales which combines 

 the long head and elongate form of BoIcb- 

 noptera with the smooth skin of the throat 

 and absence of the dorsal fin of Balcena.'* 

 This is the Gray Whale, Rhachianectes glaucus 

 of Cope, which, in these days, is confined to 

 the North Pacific, and does not range farther 

 south than the 20th parallel in that ocean. 

 At the same time it should be stated that 

 indications have been discovered that a 

 nearly allied form existed in the Atlantic 

 in previous geological ages, though this is 

 by no means certain. Besides Rhachianectes 

 Balcena, Megaplera and Balcenoptera are all 

 represented in the North Pacific, and also 

 many species of Delphinidce, of which little 

 is at present known. But Rhytina- and 

 Rhachianectes are the only genera of Marine 

 Mammals absolutely confined to Arctirenia. 



X. THE MIDDLE PACIFIC SEA-REGION, OR 

 MESIRENIA. 



The Eared Seals, Otaria, must have 

 necessarily passed through Mesirenia in 

 their passage from south to north, though 

 the only record of their recent presence in 

 the central part of the Pacific is, so far as 

 I know, the report that they were formerlj'^ 

 found in the- Galapagos. It should be 

 stated, however, that Tschudi records the 

 occurrence of two species of Otaria on the 

 islands of the coast of Peru, and that in 

 1802 Humboldt met with an Eared Seal on 

 the island of San Lorenzo, in the Bay of 

 Callao, which is only some 12° south of the 

 Equator. 



Like Otaria, the Sea-elephant {Maero- 

 rhinus) has apparently in former ages trav- 

 elled up the South American shores and 

 established itself as far north on the coast 

 of California as about 34° N. lat. The 

 California Sea-elephant has been discrimi- 

 nated by Gill as a distinct species (Macro- 

 rhinus angustirostris) , but its differences from 



* Flower and Lydekker, Mammals, p. 241. 



