OPALINID CILIATE INFUSORIANS — METCALF 599 



trans-Pacific land route between South America and Malaysia or 

 Australasia is furnished by corals, Crustacea, spiders, Mollusca, and 

 Foraminifera, chiefly by fossils of these groups; and the paleontological 

 evidence places the communication in the Eocene (see Berry, 1930). 

 Joleaud (1931) routes the trans-Pacific land bridge via Papua, Bis- 

 marck Archipelago, Marshall Islands, New Hebrides, Fiji, and Cook 

 Islands. With frequent changes in extent of its connections this 

 bridge may have existed from the late Cretaceous through, or perhaps 

 beyond, the Eocene. 



THK LEPTODACTYLIDAE (Fig. 153) 



Tropical America, both south and north of the Isthmus of Panama, 

 abounds in leptodactylids. They are well represented, a score or more 

 species, in Tasmania, Australia, and Papuasia, and are found nowhere 

 else except for a couple of forms that have spread into southern 

 Texas and perhaps one genus, two species, in South Africa. This 

 form, Heleophryne, has primitive parasites, Protoopalinas of subgenus 

 I, and these do not help solve the puzzle of the presence in South 

 Africa of a single genus, a reputed leptodactylid, so far from the 

 proper home of the Leptodactylidae. Stejneger is inclined to con- 

 sider Heleophryne a ranid with arrested development. If it is a true 

 leptodactylid its distribution is a serious puzzle. 



Judged from the great number of species and genera in tropical 

 America, that would seem the ancestral home of the family, but there 

 are reasons for questioning this. Hyla is not in Patagonia. If Hyla 

 and leptodactylids were together in Brazil, before the trans- Argentine 

 sea (?) was present, why did they not pass together to Papua and 

 Australia? Leptodactylids are in Patagonia today, and at some time 

 since Australasia separated from Asia-Malaysia they entered Aus- 

 tralasia. They are today an active, vigorous dommant family, taking, 

 in Australia and South America, a place similar to that of the Ranas 

 in other lands. Rana is not in these two continents, except for a 

 single species in the extreme north in each continent. Leptodactyhds 

 were apparently the characteristic Anura of Antarctica and connected 

 lands (Australia, Patagonia) during the early Miocene or earlier, when 

 the Antarctic climate was mHd and moist, as mdicated by its fossil 



""we may reconstruct the history of the Leptodactylidae about as 

 follows: They arose from ancestors common mth the Hylidae. llie 

 Hylidae evolved to the north of the trans-South American sea (or wlmt- 

 ever it was), which effectively separated tropical South Am.erica 

 from Patagonia, and became adapted to tropical rain-forest conditions. 

 The Leptodactylidae evolved in Patagonia, or m lands far her south 

 and west (Antarctica). Later, when they spread over all tropica 

 and south-temperate South America, they gave nse to numerous 



