Geology and Mineralogy. 483 



while from chapter III on the fauna is treated in detail. An 

 interesting table is prepared showing the percentage of speci- 

 mens obtained of each of the species represented in the collection. 

 This sums up not only the range of species but their relative 

 abundance in the fauna and suggestions as to the sort of food 

 they ate and the character of the country wherein they lived. 

 Of the general types perhaps the most interesting in view of 

 their almost exclusively South American character are the Eden- 

 tates, which, however, comprise only 8 per cent of the fauna as 

 compared to 50 per cent in the later Santa Cruz beds. They 

 seem to have been indigenous to South America, where they 

 later flourished in the greatest variety and profusion of numbers. 



Hoofed animals are abundant and peculiar, and to appreciate 

 their significance it should be borne in mind that South America 

 was geographically isolated from early Eocene until late Miocene 

 or early Pliocene time, during which a remarkable evolution 

 occurred uninfluenced by immigration from other lands. Of 

 these ungulates the most interesting were the Litopterna, paral- 

 leling in their development the horses ; the Typotheria, with 

 chisel-like front teeth and permanently growing grinders from 

 which Loomis infers a harsh diet of grass and bark, while the 

 feet seem to indicate adaptation to hard ground ; and the Toxo- 

 dontia, represented by the Nesodontidse and Leontinidse, which 

 are heavier forms, the latter being browsers living among bushes. 

 All these types, which are included under the order Notoungulata, 

 form a group with apparently a common ancestry and their rela- 

 tionships appear to the author to be with the Ilyraeoidea, which 

 are generally credited with originating in Africa. 



The Pyrotheria were very large browsing animals, the skull of 

 which is so very proboscidean in appearance that they are said 

 to be " related to the early elephants which also arose in Africa, 

 but it seems to me [Loomis] that this form came to Patagonia at 

 least at a later period, making its first appearance in the upper 

 part of the Astraponotus period. Ultimately the elephants and 

 Hyracoidea had a common origin in Africa." Scott in his " Land 

 Mammals in the Western Hemisphere " says of the grinding 

 teeth of Pyrotherium ; " These teeth are decidedly reminiscent 

 of the dentition of the aberrant proboscidean. Dinotherium, from 

 the Miocene and Pliocene of Europe, and this resemblance, 

 together with the form of the tusks, has led to the reference of this 

 group to the Proboscidea, but the assignment is undoubtedly 

 erroneous, as is shown by the character of the skull and skeleton." 

 Professor Scott is high authority, and in addition to his testimony 

 may be offered the very great difficulty of finding evidence for a 

 possible land bridge from Africa after the close of the Mesozoic, 

 and Cretaceous time seems to the reviewer too early for an immi- 

 gration of either proboscidean or hyracoidean stock. It would 

 appear, therefore, that the remarkable likenesses which Loomis 

 clearly demonstrates between the Pyrotherium and Palceomas- 

 todo?i skulls are, as in the case of the true horses and Litopterns, 

 only the result of convergent evolution. 



Am. Jour. Sci.— Fourth Series, Vol. XXXVIII, No. 227.— November, 1914. 

 33 



