
1891.] Geology and Paleontology. - 999 
It has been assumed that South America received its llamas and horses 
from North America on abundant evidence; and it is now probable 
that she received the tapirs and peccaries from the same source, since no 
early types of these lines have been revealed in South American forma- 
tions by recent extensive researches in that continent. Sloths and 
Glyptodons are, however, shown by these investigations to have 
existed in South America during the Eocene period, so that our 
primitive Glyptodont and Caryoderma may have been an early immi- 
grant from that continent, while the sloths came later. As regards 
bears, it is well known that we have not found their ancestral types in 
either of the Americas, but that they are abundantly found in the 
Neocenes of Europe and India. Arctotherium is both the earliest and 
most primitive form which we possess, and the time of their appear- 
ance is the same in both North and South America, They probably 
reached this continent at a comparatively late date, but earlier than 
the arrival of the true genus Ursus, Between the two genera occurs 
the Tremarctos, of which one species exists still in the Andes, 
T. ornatus Cuv., and one exists in the fossil state, T. etruscus, in 
Europe (Cuvier, Oss. Fossiles, Pl. 189, Fig. 8). This indicates “thie 
possible origin of the genus Ursus on the American continent, as well 
as on that of Eurasia ; but prior to Arctotherium America has nothing, 
while Eurasia has everything. —E. D. Cope. 
_ EXPLANATION OF PLATE. 
Skull of Arctotherium simum less than one-fifth natural size, linear. 
Fig. 1, profile; 2, from below; 3, from above. 
Foramina: In., incisive ; Pa., palatine; Op., optic ; So., semen 
R., rotundum; As., alisphenoid ; Ov., ovale; Pg., oid ; Ca., ; 
MA., meatus auditorius externus ; "a ., lacerum posterius ; Có., condylar ; 
Ps., postsquamosal ; Op., postparietal. 
The Work of White Ants in Australia.—In a recent 
paper 
on Central Australia, published in the Proceedings of the London 
Geographical Society, June, 1891, Mr. Charles Chewings quotes Mr. 
Woodward as authority for the statement that extensive alterations in 
the surface of the country are due to the industry of the white ants, 
Mr. Woodward has traveled over a large part of Australia, and he has 
had the especial advantage of examining the so-called desert sandstone 
formations, to the disintegration of which we attribute those endless 
sandhills that have been so often described as a dessert, but which can- 
not be strictly so called, since this sandy land is covered, often 
very thickly, with trees and shrubs. He is of the opinion that a 
Am, Nat.—November.—4. i a : 



