THE OPALINID CILIATE IXFUSORIAXS. 199 



nuclei, 0.005 mm. by 0.0055 mm. ; cilia line interval, anterior 0.00174 

 mm., posterior 0.0039 mm. 



My infections of this species show less diversity of form than is 

 seen in Ofcdina ohtrigonoidea. The largest individuals are of about 

 the same size as the smallest forms seen in infections of O. ohtrigo- 

 noidea maxima. The point of chief difference from 0. ohtHgo- 

 noidea and its several subspecies is the elongated nuclei. In the 

 resting condition they are distinctly ellipsoidal. 



OPALINA DISCOPHRYA, new species. 



Type. — United States National Museum Cat. No. 16585. 



Host. — Bufo cognatus Say, one abundant infection, from United 

 States National Museum specimen No. .37969, 89 mm. long, from Al- 

 buquerque, New Mexico, June 1, 1907; J, Hurter, collector. 



Fig. 168. — Opalixa DiscopHnxA, from Bufo cognatus^ X 117 diameters. 



Measurements of an ordinary individual. — Length of body, 0.562 

 mm.; width of body, 0.18 mm.; thickness of body, 0.05.; diameter 

 of nucleus, 0.0048 mm. to 0.0055 ; diameter of endospherule, 0.00137 

 mm.; cilia line interval, anterior 0.002 mm., middle 0.00375 mm., 

 posterior 0.0041 mm. 



Many individuals of this species have the anterior end of the 

 body of peculiar form, somewhat resembling the anterior disk of 

 Discophmja cepedei^ a feature which suggests the specific name. Ap- 

 parently in life the form of this thickened anterior end is various, 

 for in the preserved specimens some individuals show the thickening 

 greater than do others. In some cases the front of the body forms a 

 flat, oval disk. In others there is merely a ridge a little behind and 

 parallel to the anterior edge. In others there is no disk or ridge, 

 merely an ordinary oblique anterior end. It would be desirable, of 

 course, to see living animals before describing this feature of their 



