30 



SCIENCE. 



[N. S. Vol. V. No. 106. 



■without attempting any subdivision whatever — 

 and using the term ' Tropical ' in precisely the 

 sense in which ' Neotropical ' is commonly em- 

 ployed. 



Another case of unintentional misrepresenta- 

 tion occurs on page 364 with reference to the 

 peninsula of Lower California. At the end of 

 a quotation from my Presidential Address on 

 the Geographic Distribution of Life in North 

 America he says: "The proposal to form a 

 separate region for such an insignificant area as 

 the southern extremity of California seems un- 

 necessary, although its fauna may differ con- 

 siderably from that of the typical Sonoran" — 

 implying that I suggested its erection as a 

 'separate region,' whereas the rank I really 

 gave it is the trivial one of a ' subdivision ' of 

 a 'zone.' I said: "The peninsula of Lower 

 California is a subdivision of the arid Lower 

 Sonoran Zone. Not a single genus of land 

 mammal or bird is restricted to it and but two 

 peculiar species of mammals have been de- 

 scribed."* 



In the same connection it might be men- 

 tioned that the only one of my papers on the 

 life areas of North America quoted by Mr. 

 Lydekker was published in the spring of 1892. 

 Subsequent papers, containing certain modifi- 

 cations of the views expressed in 1892, together 

 with much additional matter, are not referred to. 



The part of the book which is probably of 

 greatest importance is that which treats of the 

 fossil vertebrates of South America. Mr. Ly- 

 dekker has himself visited Argentina, and 

 therefore should speak with authority. The 

 paleontological discoveries of Ameghino in 

 southern South America are of surpassing in- 

 terest. Ameghino unearthed the fossil bones of 

 a fauna which was not only previously unknown 

 but whose ancestry could not be clearly pointed 

 to in any part of the world. The subsequent 

 study of this fauna has developed some of the 

 most interesting and far-reaching problems with 

 which naturalists and geologists have had to 

 grapple. These problems relate to the ancient 

 land connections of South America and to the 

 origin and lines of evolution of important 

 groups of mammals and birds. 



*Proc. Biol. Soc. Washington, VII., p. 29, April 

 1892. 



Our own distinguished paleontologist, Prof. 

 W. B. Scott, in an address delivered a year ago 

 before the Society of American Naturalists, 

 stated that the earlier Miocene mammals of 

 South America "are totally different from those 

 of the northern land-masses, so much so that 

 the correlation of horizons becomes a matter of 

 extreme difficulty. The hoofed animals all be- 

 long to orders unknown in the north — Toxo- 

 dontia, Typotheria, Litopterna — and the princi- 

 pal constituents of the fauna are immense 

 numbers of Edentates, Marsupials and Rodents, 

 with several platyrrhine monkeys. No artio- 

 dactyls, perissodactyls, proboscidians, Condy- 

 larthra or Amblypoda, neither Insectivora, 

 Cheiroptera, Carnivora or Creodonta are known. 

 The Edentates are all of the specifically South 

 American type, sloths, armadillos and the like. 

 The Eodents also are very much like those 

 which still characterize the region, though 

 most of the genera are distinct ; they are all 

 Hystricomorpha, neither squirrels, marmots, 

 beavers, rats or mice, hares or rabbits occur- 

 ring among them." (Science, February 28, 

 1896, 808.) 



The total absence of the early South Ameri- 

 can types from the rich deposits of vertebrate 

 fossils in the United States, and the correspond- 

 ing absence of North American types from all 

 but the later fossil beds of South America, prove 

 clearly, as Mr. Lydekker says, that "there 

 must have been a barrier between North and 

 South America during the Oligocene and a por- 

 tion or the whole of the Miocene." Scott has 

 already told us that "in the Pliocene (Monte 

 Hermoso) appear the first traces of the union 

 with North America, in the presence of masto- 

 dons, horses, tapirs, deer, llamas and true car- 

 nivores, and from that time till far into the 

 Pleistocene the intermigrations between the two 

 continents kept up until a large number of com- 

 mon types had been established." Lydekker, 

 speaking of the same event, says : " The pres- 

 ence of a glyptodont in the Nebraska stage of 

 the Loup-Fork group in North America, and of 

 northern forms in the Monte Hermoso horizon 

 of South America, marks, then, the first com- 

 mingling of the original faunas of the two halves 

 of the New World. For the first time in the 

 history of the southern continent this connec- 



