376 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



Asia, and there have been late Tertiary migrations between other 

 originally Equatorian lands and Arctogea — from India northward, 

 and from Euro-Asia soutliAvard into Africa. 



The paleontological evidence as to the times and places of origin 

 of the Anura and their several groups is very scant, a fact not easy I 

 to understand. Oxyglossus^ one of the Raninae, is reported from 

 Wyoming in a deposit whose age is given as Eocene by Gadow 

 (1909) , and as Comanchian by Schuchert (1915), but this is very dif- 

 ficult to accept. Palaeohatrachus, which seems to be similar to the 

 Pipidae, is reported from the mid-Tertiary from Europe (Gadow, 

 1909). Bufo serratits and B. gessneri are reported from Oligocene 

 and Miocene rocks from Europe (Gadow, 1909). The Anuran fossil, 

 Oxyglossus^ reputed to be the earliest known, is said to be a member 

 of probablj' the most highly evolved family. It is not surprising, 

 therefore, to find that evidence from the distribution of their char- 

 acteristic parasites, the Opalinidae, puts the origin of the Anura 

 back at least to the Triassic, two geologic periods earlier than the 

 earliest date claimed for any Anuran fossil. 



What groups of the Anura are to-day dominant and what ones 

 seem to be disappearing? This question is of interest in weighing 

 the evidence presented by the distribution of the several groups. 

 The Pipidae seem an archaic family not particularly successful to- 

 day. The Discoglossidae seem to be disappearing. The Pelobatidae 

 have adopted retiring habits and are persisting, but show no great 

 vigor as conquerors of the earth. The Gastrophrynidae are nowhere 

 dominant now, but they show no special indication of being on the 

 wane. The Leptodactylidae, the Hylidae, the Bufonidae, and the 

 Ranidae are all in full vigor and are important elements in the 

 faunas of their several habitats. 



In all this review of the hosts and the geographical distribution 

 of tJie Opalinidae, we see that there are limitations to the dispersal 

 of the several groups of parasitic species both in the families of their 

 hosts and geographically. We have regarded Protoopalina as the 

 most archaic genus of Opalinidae, Zelleriella as more modified, 

 Cepedea as further modified in another direction, and Opalina as the 

 most modified genus of the family, though considered from the stand- 

 point of the inhibition of division, Cepedea segmentata would be the 

 most highly evolved species in the family. Viewed in the broad, 

 there is a rather curious parallel between the relative degrees of 

 evolution of the hosts and of their parasites. The Protoopalinas are 

 found in fishes and Urodeles (probably modern infections), and are 

 well represented in the lower families of Anura, being found also in 

 a good many species of the higher Anuran families. The Zelleriellas 

 are not well represented in the lower and the highest families of 



