woodruff: rhizopoda of Kansas. 203 



Psds. slender, cylindrical, simple or branched. Species is a common one 

 and many varieties of shells are included in it. Plates XXIX, XXXI, 

 XXXII; figs. 1, 2, 5, 6, 9, 10, 19, 22, 28, 31. 

 Diffiugia arcula. 



Shell hemispheroidal; fundus convex, base inverted shallow infundi- 

 buliform; mouth mferior, central, trilobed. Structure of shell usually 

 of yellowish chitinoid membrane, usually with more or less adherent dirt 

 or scattered particles of quartz sand or diatoms, especially occupying 

 the fundus. Plate XXIX; fig. 11. 

 Diffiugia acuminata. 



Shell usually composed of sand crystals, oblong oval in shape, the 

 fundus prolonged into an elongated process more or less acuminate; no 

 spines. Great variations may occur in the size and shape of the shells. 

 The posterior acuminate process, although a characteristic of this species, 

 may be possessed by other species. Mouth large, terminal, circular. 

 Plate XXXI, fig. 18; plate XXXII, fig. 26. 

 Diffiugia constricta Leidy. 



Shell oval in form with the anterior border obliquely truncate, com- 

 posed of sand grains and other foreign materials. Fundus rounded, with 

 or without spines. If present the number of spines may vary from one 

 to half a dozen. Mouth lai-ge, circular or oval, and inverted. Shell color- 

 less, yellowish or brown. Sarcode colorless. Plate XXX; fig. 15; plate 

 XXXI, figs. 23, 24. 

 Diffiugia urceolata. 



Shell of large size, fundus usually evenly i-ounded, seldom spined; 

 neck short; mouth large, circular, surrounded by a reflected rim with 

 a thin edge. Pseudopods as in pyriformis rarely branched. (Length 

 250-300 microns.) Plate XXXI, fig. 2.5; plate XXXII, fig. 27. 



Pseitdodiffi-ugia. 



Shell chitinous, to which foreign materials are added. Pseudopodia 

 delicate and branched. Sarcode mostly colorless, with large clear nucleus, 

 but usually with sarcode obscured by the nature of the shell. Mouth 

 terminal, inferior. 

 Pseudodifflugia gracilis. 



Shell of variable form, mostly spheroidal, ovoidal, or oblong oval 

 and of uniform transverse diameters, usually straight, occasionally 

 slightly curved. Mouth terminal, circular. Structure of shell mostly 

 obscurely granular, often of fine sand, frequently almost entirely com- 

 posed of coarse sand, colorless or brownish. Found in ooze of ponds, 

 ditches, etc. Plate XXXII, figs. 34, 35, 36. 



Arcella. 



Arcella Ehr. 



Body secretes a shell of chitinoid material, semispheroidal in shape 

 when viewed laterally, usually circular when viewed dorsally or ven- 

 trally. Mouth central. Psds. digitate or broadly lobate, never branched. 

 Nuclei and C. Vac. usually more than one. 

 3— Univ. Sci. Bull., Vol. VII. No. 9. 



