230 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



OPALINA RANARUM, form ARVALIS, new forma. 



Type. United States National Museum Cat. No. 16598. 



Ilost. — Rana arvalis Nilsson, one abundant infection, from United 

 States National Museum frog No. 37177, 55 mm. long, from Lower 

 Austria, September, 1895 ; F. Werner collector. 



Fig. 203. — Opalina ranardm, form akvalis, x 117 diameters. 



Measurements of an average individual. — Length of body 0.26 

 mm.; width of body 0.145 mm.; thickness of body, anterior 0.016 



mm., middle 0.022 mm., pos- 

 terior 0.021 mm. ; diameter of 

 nucleus 0.005 mm. to 0.0065 

 mm.; diameter of endospher- 

 ule 0.002; cilia line interval, 

 anterior 0.0018 mm., posterior 

 0.0042 mm. 



The Opalinas in this infec- 

 tion differ from those from 

 Rana dalmntina in being 

 more pointed behind, and in 

 being thinner in front than 

 behind. In the latter regard 

 they differ from all other 

 specimens of 0. ranaruni I 

 have measured, except the form lata^ next to be described. This dif- 

 ference seems to justify classing them as a distinct forina. 



OPALINA RANARUM, form LATA, new forma. 



r?/;?e.— United States National Museum Cat. No. 16603. 

 Host.—Bufo viridis Laurenti, numerous infections from Naples, 

 Italy, April, 1907 ; M. M. Metcalf collector. 



Fig. 204. — Opalina ranarom form lata, X 117 



DIAMETERS. 



