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THE AMERICAN NATURALIST 



[Vol. XLVI 



The separation of Madagascar from Africa has permitted the 

 continuance of the relatively large Centetidse, the tenrecs, of 

 which Ericulus, Centetes and Hemicentetes have developed a 

 spiny coat and Limnogale has become aquatic. Similarly, the 

 rare and interesting Zalambdodont, Solenodon, has been able to 

 continue an existence by isolation in Cuba and Hayti. Even 

 thus isolated, Solenodon, judging from its extreme rarity, barely 

 maintains a foothold. The aberrant Tupaiidse, or Oriental tree 

 shrews, are, as indicated by their name, arboreal and the African 

 Macroscelididae, or elephant shrews seek refuge by leaping and 

 by skulking. The South African Chrysochloridae, or golden 

 moles, and the familiar Talpidae are subterranean. A subter- 

 ranean habitat implies a restricted stature. Erinaceus, the well- 

 known hedgehog, and the African Potamogale, the only rela- 

 tively large non-insular insectivores, are well protected, the 

 former by its spiny coat and the latter by its aquatic habits. 

 The Soricidae containing the smallest members of the order are 

 largely nocturnal. During the long stretch of time since the 

 Eocene culmination of the group and the gradual evolution of 

 more modern mammalia, the Insectivora have become extinct 

 with the exception of those especially protected, insular, sub- 

 terranean or of insignificant size. Smallness here seems an 

 attendant trait of archaism. The earliest American mammals, 

 the Triassie Protodonts, Dromatherium and Microconodon and 

 among recent mammals certain Murine rodents closely simulate 

 this diminutive stature. 



The massive Rorqual whale, Balcenoptera sibbaldii Gray, of 

 the North Atlantic, sometimes reaching a length of eighty-five 

 feet, is the bulkiest vertebrate which has ever existed. The 

 Cetacea are likewise a primitive and probably degenerate group. 

 Other aquatic mammals, such as the Sirenia, Pinnipedia, etc., 

 similarly reach immense proportions, due, very likely, to the lack 

 of a compensatory element in the environment. The tallness of 

 the giraffe, which is an adaptation to arboreal grazing, produced 

 by an elongation of the cervical vertebrae, coordinated of course 

 with limb structure, has independently arisen in at least one 

 other family. The giraffe-camels of the genera Oxydactylus and 

 Alticamelus, respectively, of the American Oligocene and Mio- 

 cene, parallel the existing giraffes. 



The smallest known bird is Calypte helence (Gundlach) of 



