490 PKOCEEDINGS OF THE NATIOIsrAIj MUSEUM 



Measurements, in microns: 



VOL. 87 



Measurement 



6 (divid- 

 ing) 



Length of body__ 

 Width of body___ 



Nucleus length 



Nucleus width __ 

 Cilia line interval. 



180 

 130 



124 



148 



25 



10 



152 

 100 



20 



18.5 

 3.9 



Many of these Zelleriellas show numerous cytoplasmic parasites, 

 the amoebae (Stabler and Chen, 1936), which were not studied. 

 This species is thinner behind than in the front part of the body, but 



Figure U.—ZeUeriella dvbia, new species: a, X 59; 6, X 230; c, X 505. In c the six smaller bodies are 

 parasites. Further work of Stabler and Chen (1936) shows that they are amoebae. 



the posterior edge is not quite so conspicuously thin as in some forms 

 of the genus Opalina, e. g., 0. ranarum form truncata (Metcalf, 1923a). 

 This large Zelleriella is of different form from Z. magna. It differs 

 from the opisthocarya group in the more anterior position of its nuclei. 

 None of the specimens shows so definite a posterior point as does Z. 

 patagoniensis. It is much larger and has relatively much larger 

 nuclei than Z. brasiliensis. Studying whole infections, shape, size, 

 and measurements, I am impressed that it is a distinct species, if 



