354 BULLETIN" 120, UNITED STATES NATIONAL MUSEUM. 



end is usually not sharp pointed or even narrow pointed, but is well 

 rounded or even indented. In the table on page 347 the slender spe- 

 cies, some of whose individuals approach the ranarum group in shape, 

 are indicated by the annotation "[Z ?] " Of these O. guatemalae be- 

 longs apparently to the Opalinae angustae^ so do 0. ohtrigonoidea 

 orhiculata^ O. terrae-mariae^ O. riioreletei, 6>. sp. (?) from Bufo hae- 

 Tnatiticus, and 0. copei. On the other hand. O. gigantea and O. 

 draytonii, though western species, are broad. Opalina pancumen»is 

 may also be an immigrant broad species. We may say that the west- 

 ern species of Opalina are in general slender, or at least pointed 

 behind, though some species show individuals which are broader 

 throughout or not pointed behind. 



On the other hand, omitting from consideration the problematic 

 Opalina virgula, all but one of the known Eastern Hemisphere spe- 

 cies of Opalinae are Opalinae latae. They occur, 1, in Bufo from 

 Europe across to eastern Asia in the species B. hufo and its sub- 

 species asiaticus, in B. viridis and in B. smithi; 2, in Ranidae, includ- 

 ing (2, Eanas from Europe, temperate Asia, southeastern Asia, and 

 Java, also one Kana from the African Gold Coast; &, a Hylambates 

 from the Cameroons ; and c, a Phrynohatrachus from the Sudan. The 

 Opalinae latae are thus seen to occur in Europe, Asia, and Africa. 

 They are not known from Madagascar, Australasia, or South 

 America. Two, or probably three, broad forms {0. draytonii, 0. 

 gigantea, and probably 0. panamensis) occur in North America and 

 Central America. It seems that these are immigrants from Asia by 

 way of Bering Straits. Other American species which show some 

 broad individuals show also other narrower individuals which indi- 

 cate affinity with the Opalinae angustae. 



The line of demarcation between the Opalinae anguatae and the 

 Opalinae latae is not a sharply indicated one, but it is clear that the 

 eastern species are broad and the western species are in general nar- 

 rower. It is also clear that the Opalinae are of northern origin and 

 have not extended to any degree to the southern hemisphere except 

 as recent immigrants into Africa. 



Opalina doubtless evolved from Cepedea and so, of course, is more 

 recent. The Ranidae and the species of the genus Bufo are to-day the 

 chief hosts of the eastern Opalinas {Opalinae latae) and in either 

 the Ranidae or, less probably, Bufo the broad Opalinas may well 

 have evolved. Rana, Bufo, and especially the North American and 

 Central American Hylidae are to-day the chief hosts of the western 

 Opalinas {Opalinae angustae). Apparently in one of these three 

 groups, probably in the Hylidae, these narrow western forms first 

 arose. Their evolution in some Hylid, rather than in Bufo or a Ea- 

 nid, is probable, for they are not known in Bufos or Ranids except 



