. The geography of mammals. hichalthough, in some cases, at the present day entirely fluvia-tile, must probably have descended from oceanic three known genera are Platanista of the Gangesand Indus (Fig. 48), Inia of the river Amazon, andPontoporia of the river La Plata; the last form making 1 Sir William Flower (Whales, Past and Present, Proc. Roy. Inst,x., p. 360, 1883) rather favours the idea of a freshwater origin of theCetaceans. MARINE MAMMALS 207 a connecting link between the two preceding genera andthe marine Dolphins. The third family of Toothed Whales, containing theDolphin
. The geography of mammals. hichalthough, in some cases, at the present day entirely fluvia-tile, must probably have descended from oceanic three known genera are Platanista of the Gangesand Indus (Fig. 48), Inia of the river Amazon, andPontoporia of the river La Plata; the last form making 1 Sir William Flower (Whales, Past and Present, Proc. Roy. Inst,x., p. 360, 1883) rather favours the idea of a freshwater origin of theCetaceans. MARINE MAMMALS 207 a connecting link between the two preceding genera andthe marine Dolphins. The third family of Toothed Whales, containing theDolphins, Delphinidte, is very numerous in species andembraces at least fifteen or sixteen genera, of which theCommon Dolphin (Fig. 49) is a good example. But inspite of the efforts of Mr. True, who has recently givenus an excellent summary of our present knowledge ofthem,1 both the genera and species of Delphinidss are stillso imperfectly understood that not much can be saidabout their geographical distribution. Most of the forms. Fig 49.—The Common Dolphin. (Delphinus delphis.) [Flower and Lyd. Mamm., p. 271.] appear to be very widely distributed, but it may be saidgenerally that Dolphins are most abundant in the inter-tropical seas and less plentiful both to the north andsouth of them. There are, however, two forms that are exclusivelyinhabitants of the Northern Oceans. These are the veryremarkable Narwhal (Monodon), in which the male isfurnished with a single enormous horn-like tusk, and theBeluga, or White Whale (Delphinapterus), closely allied i See A Review of the Family Delphinidse, by Frederick W. Nat. Mus., No. 36 (Washington, , 1889). 208 THE GEOGRAPHY OF MAMMALS to the Narwhal in many points of its general structure(Fig. 50). These may be looked upon as quite isolated
Size: 3427px × 729px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookidgeogra, booksubjectmammals
