788 



SCIENCE 



[N. S. Vol. XL. No. 1039 



events in the history of the mammaliaxi 

 stocks. 



The hulk of the book is taken up by a sum- 

 mary of the extinct mammals; first those 

 without the placenta (Eplacentata), or the 

 marsupials, including the Allotheria or multi- 

 tuberculates, the African Tritylodon, Ptilo- 

 dus and Polymastodon of North America, and 

 the various types described by Ameghino from 

 Patagonia. After these comes a discussion 

 of the diprotodont marsupials in Australia 

 and South America, vchile the triconodonts 

 are included v?ith the polyprotodont types. 

 Placental mammals embrace the Pantotheria 

 or trituberculates and all forms above them, 

 of which the insect-eating types or Insectivora 

 are the most primitive; the author also in- 

 cludes under this head the unique Tillodonta, 

 Tillotherium and its rare allies, whose posi- 

 tion in the mammalian scheme is very doubt- 

 ful. The relationships of the creodonts and 

 fissipede Carnivora are clearly set forth, after 

 which Abel describes the ancient whales. 



The group of edentates are discussed under 

 two distinct heads, the Xenarthra or " poor- 

 toothed " mammals of South America, and 

 the Nomarthra, those of the Old World, of 

 which there are relatively very few. Rodents 

 are briefly dismissed, the curious horned 

 types, Epigaulus and Ceratogaulus, of the 

 Miocene of Colorado and Kansas being em- 

 phasized as the most remarkable. 



The hoofed mammals are always the most 

 conspicuous and numerous forms in every 

 fossil fauna, and to them the greater part of 

 the volume under consideration is devoted. 

 Twelve orders are recognized, of which the 

 first is the " Stammordnung " Protungulata, 

 embracing all of the forms usually included 

 under the order Condylarthra and certain ad- 

 ditional families such as the Pantolambdidse, 

 here considered as ancestral to the Amblypoda 

 instead of being placed under that order as is 

 the usual custom. The Bunolitopternidae, 

 ancestral to the Litopterna, are also placed 

 here. 



Following the ungulates, the primates are 

 discussed, but a very brief section only is 

 given to fossil man. 



The final chapter of the book is upon the 

 rise, dominance and decline of the mammal- 

 ian stem. Of particular interest is the au- 

 thor's discussion of the causes of extinction, 

 great emphasis being laid upon the possibil- 

 ity of contagious diseases having an exten- 

 sive influence in the extinction of faunas. 



Altogether the book is a well-balanced pro- 

 duction which avoids excessive technicalities 

 but gives a very good general idea of the more 

 essential facts of mammalian anatomy, classi- 

 fication and relationships as disclosed by 

 paleontology. It shows, moreover, how neces- 

 sary for systematic work in recent zoology an 

 adequate knowledge of extinct animals has 

 become. An interesting commentary upon 

 the advancement of paleontological science is 

 afforded by the fact that the great bulk of il- 

 lustrative material is drawn from American 

 authorities and based upon the fossil re- 

 sources of the New World. 



ElCHARD SWANN LULL 



Tale University 



THE vegetation OF THE NEBRASKA SAND HILLS 



The average traveler regards the prairies 

 and plains as regions of extreme monotony; 

 particularly is this true if his way takes him 

 through a region of sand hills. The total in- 

 correctness of this view is admirably illus- 

 trated by the publication of Professor Pool's 

 researches in the Nebraska sand hills.^ From 

 an earlier and semi-popular presentation by 

 the same author we had learned to know 

 something of the fascination and scientific 

 interest of these dynamic landscapes, and now 

 we have his detailed results.^ 



The Nebraska sand-hill country covers an 

 area of about 18,000 square miles, that is, 

 nearly a fourth of the area of the state. There 

 are similar but smaller areas of sand hills in 

 Kansas, Colorado and the Dakotas. The soil 



1 " A Study of the Vegetation of the Sand- 

 hills of Nebraska," Eaymond J. Pool. Minn. 

 Bot. Stud., III., 4: 189-312, pis. 15, figs. 16, 

 map 1, 1914. 



2 ' ' Glimpses of the Great American Desert, ' ' 

 Eaymond J. Pool. Pop. Sci. Mon., 80: 209-35, 

 figs. 17, 1912. 



