February 28, 1896.] 



SCIENCE. 



317 



mammal families derived from studies of 

 northern strata and in part on the identifi- 

 cation of mammal remains of Patagonian 

 strata with Dasyurids, but this evidence 

 may prove illusive. Of some importance in 

 estimating the age is the rediscovery by 

 Mr. Thomas after 20 years of the Hyra- 

 codon of Tomes and its reference to the 

 supposed extinct familj'' of Epanorthids. 

 This evidence, however, is by no means 

 conclusive. Eather violent assumptions be- 

 come necessary of remarkable dj'namical 

 conditions and the peopling of the said con- 

 tinents by the same type may be hereafter 

 explained otherwise. But in the present 

 condition of our knowledge (or ignorance, 

 if you will) , less violent assumptions ap- 

 pear to be called for bj^ the hypothesis that 

 has now been presented than by any other. 

 It must be distinctly understood, however, 

 that it is a hypothesis and a tentative hypo- 

 thesis only. But until it is replaced by a 

 better one or by ascertained facts, the hj'po- 

 thesis will assuredly be useful in directing 

 investigation. 



Vertebrata of the Land ; Birds and Mammals. 

 By De. J. A. Allen, American Museum 

 of N"atural History, New York. 

 So far as existing mammals and birds are 

 concerned, there seems to be verj^ slight 

 need for calling in the aid of a former Ant- 

 arctic continent to explain their present dis- 

 tribution. Among mammals the distribu- 

 tion of Marsupials alone gives a hint of a pos- 

 sible former land connection between South 

 America and Australia. The recent dis- 

 covery (Thomas, Ann. and Mag. Nat. Hist. 

 (6) XVI., Nov. 1895, p. 367) of a form of 

 Marsupial in Colombia belonging to the 

 hitherto supposed extinct family Epanor- 

 tliidse, and the occurrence of several dis- 

 tinctly Australian types among the fossil 

 Marsupials of Patagonia, would seem to add 

 much emphasis to this hint. On the other 

 hand, the absence of all other South Amer- 



ican types of either mammals or birds from 

 the Australian region, and the presence of 

 the remains of numerous opossum-like ani- 

 m3,ls in the Eocene of both North America 

 and Europe, suggest a possible line of exten- 

 sion by way of the northern land masses 

 without the aid of any former land bridges 

 in the southern hemisphere. Possibly 

 worthy of consideration here is the wide 

 distribution of Mesozoic mammals and the 

 probable Marsupial affinities of at least 

 some of them. 



In regard to birds, after excluding wide- 

 ranging types, which have no bearing on 

 the subject in question, there are no groups 

 common to South America and either 

 Africa or Australia. The distribution of 

 the so-called Eatitfe and other flightless 

 birds so often cited as evidence of a former 

 Antarctic continent, has really very little 

 bearing on the question. The so-called 

 sub-class Eatitse includes, according to the 

 best recent authorities, no less than six 

 orders, of which the South American rheas 

 (Rhese) form one, and the only one found 

 in the New World; the ostriches of Africa 

 form another (Struthiones) , which in 

 Pliocene times ranged as far north and 

 east as southern Europe and India; the 

 kiwis of New Zealand form a third (Ap- 

 teryges); the cassowaries and emus of the 

 Australian region a fourth (Megistanes) ; 

 the recently extinct genus jEpyornis of 

 Madagascar a fifth (Aepyornithes), and the 

 recently extinct moas of New Zealand a 

 sixth (Immanes). The prevalent notion 

 that all these forms are closely related and 

 must have had a common origin doubtless 

 rests on such superficial resemblances as 

 large size and flightless condition. 



Mainly for the same insufficient reason it 

 is the fashion to refer to the E.atit£e such 

 little known extinct forms as Gastornis and 

 Dasornis of Europe, Diatryma of North Amer- 

 ica, and Brontornis, Phororhacos, Pelyeornis, 

 Opisthodaetylus, etc., of Patagonia. Although 



