THE OPALIXID CILIATE IXFUSORIAXS. 



67 



Measurements of an ordinary individual. — Length of body 0.14 

 mm. ; width of body 0.065 mm. ; thickness of body 0.026 mm. ; length 

 of nucleus 0.0142 mm.; width of nucleus 0.012 mm.; diameter of 

 endospherule 0.0012 mm. ; cilia line interval, anterior 0.0022 mm., 

 middle 0.0028 mm., posterior 0.0037 mm. 



The body of this Protoopalina is ovate, or obovate, in face view 

 and considerably flattened, its thickness being about one-third of its 

 width. The posterior end is often slightly, but definitely, pointed, 

 and in some cases the position of the excretory pore is indicated by 

 a funnel-shaped depression at the base of this point. The axial ex- 

 cretory organ is usually well developed, 

 its relation to the nuclei being clearly 

 seen. The two nuclei are almost, but not 

 quite, spherical, their long axes being 

 just noticeably the greater. Their in- 

 ternal structure is not clear in my ma- 

 terial. 



The considerable flattening of this 

 species suggests a transition toward the 

 condition of the Zelleriellas (to be de- 

 scribed later) , and this transitional con- 

 dition is emphasized still more by the 

 conditions in Protoopalina xyster and 

 Zelleriella telniatohii, to which we will 

 now turn. 



PROTOOPALINA XYSTERr" new species. 



Type. — United States National Mu- 

 seum Cat. No. 16497. 



Host.— Gastrophry lie usta (Cope), 

 one abundant infection from United 

 States National Museum specimen No. 

 10021, female with eggs, from Tehuantepec, Mexico ; F. Sumichrast, 

 collector. 



Measurements. — Length of body 0.197 mm.; width of body 0.093 

 mm.; thickness of body, anterior quarter 0.026 mm., middle 0.034 

 mm., posterior quarter 0.0466 mm.; length of nucleus 0.023 mm.; 

 width of nucleus 0.0163 mm. ; length of endospherule 0.00175 mm. ; 

 width of endospherule 0.0012 mm. ; cilia line interval, anterior 0.0022 

 mm., middle 0.0028 mm., posterior 0.0037 mm. 



This interesting species shows many individuals with the posterior 

 end of the body cylindrical, while the anterior end is widened, the 

 wider region being sharpened to an edge toward the front, like a 

 wedge. It is shaped much like a neolithic hand adz or scraper, and 



Fig. 38. — Protoopalina ovoidea, 

 X 460 diameters. 



^ Greek b ivar-np, a scraper, because of resemblance in form to a neolithic scraper. 



