308 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



ting many salient phenomena. It is evident that in referring our dis- 

 tribution data in the present paper to the charts selected we are really 

 far from giving the subject adequate treatment. In our discussion we 

 are interested chiefly in intercontinental connections and in climates 

 and the influence of these two factors upon the spread of the forms 

 we are studying, and it is upon these points that critical attention 

 should chiefly be focused. It seems unwise for a zoologist who has 

 little familiarity with paleogeography to attempt critical review of 

 these geographic data. This is purposely left to more competent 

 students, with the expectation that our tentative conclusions may be 

 modified in numerous instances. 



In the discussions in this section we will treat the data first chiefly 

 from the point of view of the Opalinidae, then from the standpoint 

 of their Anuran hosts, and later will refer to a number of matters 

 whose discussion must use both viewpoints simultaneously. But 

 this classification can not be followed with any rigidity, for the data 

 from the two groups are so interwoven and their implications are so 

 interdependent that neither aspect of the matters involved can be 

 followed exclusivel}^ in any part of the discussion. The tabulation 

 of the detailed infection and distribution data from the point of view 

 of the hosts is placed in the next section, 8, and following this will be 

 given some summary statements. 



The Opalinidae are found in the recta or intestines of Anura, 

 Urodela, and Pisces. They are known from one fish only. Box hoopSj 

 from the Mediterranean Sea. Among Urodela they have been re- 

 ported from three species only, Tritui^s vulgaris [Triton taeniatus] , 

 and T. alpestris from Europe, and Amby stoma tigrinum from central 

 North America. All other Opalinids known are reported only from 

 Anura. Only Protooyalina is laiown from hosts other than the 

 Anura, except for Galli-Valerio's (1907) report of an Opalina from 

 Triturus alpestris (quite possibly a temporar}^ infection). The 

 species in the fish. Box hoops^ is Protoopalina saturnalis: the species 

 from Tnturus vulgaris is P. ^^intestinalis'''' (it is desirable to reob- 

 serve this form) ; the species found in T. alpestris is Opalina ra.narum; 

 the species from Amhy stoma is Protoopalina mitotica. The Pro- 

 toopaiinas we have regarded as the most primitive of the Opalinidae. 

 It is of interest that it is this most archaic genus which has repre- 

 sentatives parasitic in the widest range of hosts. Among the Anura, 

 Protoopalina is known from the Pipidae, the Discoglossidae, the 

 Pelobatidae, the H3didae, the Bufonidae, the Leptodactjdidae, the 

 Gastrophrynidae, and the Kanidae; that is, from all the families 

 from which any Opalinids have been reported. Opalinids have not 

 as j-et been reported from the following subfamilies of Anura : Pi- 



