GEOGRAPHICAL DISTRIBUTION. 35 
the Upper Cretaceous. In England species existed during the Eocene and a species 
of the same epoch has been described from India as a FH ydras pis, a genus now 
existing in South America. It is worthy of note, too, that in North America the 
Pleurodires apparently disappeared long before the Amphichelydia did, the stock 
that gave origin to the Pleurodires. The Amphichelydia continued on into the 
Bridger and the Uinta. 
It will be observed from the map (fig. 16) that the Trionychide occupy the 
habitable portion of North America east of the Rocky Mountains; Africa south of 
the Sahara Desert; Asia south of the Sayanskii and Yablonoi Mountains and 
between the Persian Gulf and the Caspian Sea; and most of the East Indian islands, 
including New Guinea. Altho the oldest-known representatives of the Trionychide 
have been found in the middle of the Upper Cretaceous of North America and altho 
that continent is still inhabited by at least 6 species, it is Asia that furnishes the 
greatest number of living forms of the family, at least 15 species having been 
described from that region, including the islands appertaining to it. In Africa there 
occur about 6 species, so far as now known. As in the case of the Cryptodires, the 
trionychids have prest southward close to Australia, without having succeeded in 
7 
Fic. 16.—Map showing the distribution of the Trionychide. 
reaching it, Pelochel ys cantoris having been reported from New Guinea. No Triony- 
chide have been found in the Tertiary beds of the Fayum, Egypt. Considering 
the fact that true trionychids antedate known pleurodirids, it appears strange that 
the former were not able to reach Australia with the pleurodirids; more especially 
since the trionychids are, and have been since the Judith River epoch, excellent 
swimmers. A problem fully as hard to solve is the absence of trionychids from the 
continent of South America. So far as we can judge, they might easily, within 
rather recent geological times, have made their way thither from North America. 
Again, Ameghino has described what he regards as a species of T rionyx from the 
Cretaceous of Patagonia. The description 1s very brief and no figures have been 
furnisht. If representatives of the superfamily had reacht the continent by the 
time of the Upper Cretaceous it is remarkable that they were not able to maintain 
themselves there. No region appears to be better adapted than this for river-loving 
species of turtles. ; 
In Europe we have another illustration of the fact that animals may be driven 
from a region in which they have once obtained foothold. No species of the 
superfamily now occupies that region; but numerous species did exist there during 
the Eocene, the Oligocene, and the Miocene. It has not yet been determined 
what the influences were that operated against them. 
