THE OPALINID CILIATE IXFUSORIANS, 



319 



Group 6 (fig. 244). 



P. filifonnis (p. 56) in Rana East Indies. 



P. tenuis (p. 58) in Leptodactylidae Australia. 



P. africana (p. 60) in Rana tropical Africa. 



These are very slender, elongated, vermiform species. The first 

 two are very similar; the African form is somewhat less elongated 

 and it differs from the others in being pointed behind. It may per- 

 haps have been derived from different ancestral stock from that 



