140 FRESH- WATER EHIZOPODS OF NORTH AMERICA. 



Associated with Hyalosplienia tincta, I observed a number of speci- 

 mens, of the same sizes, variations in form, and color, but in which the shell 

 exhibited more or less evidence of areolation. In some, the appearance 

 was exceedingly indistinct; in others, it was quite positive, and these latter 

 had then all the characters of a species of another genus, which I have 

 named Nebela flabellulum. Those with the indistinct appearance of areola- 

 tion weie evidently transitional varieties toward the latter. 



I have observed sufficient variation in specimens to suspect it probable 

 that Hyalosplienia tinda merges into H. cuneata, and likewise into H. elegans 

 and H. papilio. 



HYALOSPHENIA ELEGANS. 



Plate XX, figs. 19-29. 

 Difflugia (Catharia) elegans. Leidy: Proc. Ac. Nat. Sc. 1874, 156; 1875, 415. 



Shell compressed flask-shaped; in the view of the broader side, with 

 an oval body and long cylindroid neck, slightly widened at the oral end, 

 which is convex downward; in the view of the narrower side, long elliptical, 

 and tapering to the oral end, which is deeply notched. Shell composed 

 of pale brownish, transparent, structureless, chitinoid membrane, which is 

 impressed Avith longitudinal rows of hemispherical pits. Sarcode colorless, 

 attached by threads to the sides and fundus of the shell; pseudopods digi- 

 tate, usually three or four in number. 



Size.— Length from 0.088 mm. to 0.108 mm.; breadth of body 0.064 to 

 0.01 mm.; thickness of the same 0.02 to 0.028 mm.; breadth of neck and 

 oral end 0.016 to 0.02 mm.; short diameter of oral end 0.008 mm. 



Locality. — Abundant, in association with Hyalosplienia papilio, in sphag- 

 num in the same localities. 



Hyalosphenia elegans, figs. 19-29, pi. XX, a common and graceful 

 form, living among sphagnum, appears to be quite distinct from the pre- 

 ceding species. The shell is compressed flask-shaped. Viewed on the 

 broader side, the outline of the body is oval and more or less tapering into 

 a rather long cylindroid neck. The fundus is convex, and the oral end is 

 slightly expanded and convex downward. In the view of the narrower 

 side, the shell presents a long elliptical outline, tapering to the oral end, 



