228 



FRESH-WATER BIOLOGY 



99 (98) Small size; foreign elements small. 



Phryganella hemisphaerica Penard 1890. 



Shell hemispherical, composed of small diatom shells 

 and sand grains. Pseudopodia usually slender, some- 

 times thick. Found in the ooze of ponds and lakes. 

 Diameter 40 to S5 M- 



Fig. 321. Phryganella hemisphaerica. X 250. (After Penard.) 



100 (97) Shell chitinous, without or sparsely covered with foreign ele- 



ments. . . ... lOI 



loi (102) Shell occasionally with foreign elements attached. Aperture ter- 

 minal. Cryptodifflugia Penard. 



Representative species. . Cryptodifflugia oviformis Penard 1890. 



J^ This species has a transparent, yellowish or brownish shell without foreign 



/&m elements attached. Ovoid in form. The protoplasm does not fill the shell and 



lTt\ pseudopodia are seldom extended. Found in marshes. Length i6_to 20 >i. 



^*»»J^ Fig. 322. Crypiodi^ugia oviformis. X 450. (After Penard.) 



102 (loi) Shell without foreign elements. 



Aperture terminal or subterminal. 

 Platoum F. E. Schultze. 



In 187s Schultze described a form under the na.me Flatoum panmm. 

 Ovoid with smooth envelop without structure, sUghtly elastic, aper- 

 ture terminal or subterminal. Penard, more recently, observed 

 numerous empty shells and inactive organisms which he provision- 

 ally refers to this genus. Some had undulating envelopes with 

 apertures terminal or directed obliquely. Nucleus and contractile 

 vacuole each single. Pseudopodia not observed. Length 16 to 21^. 



In preserved material from Alaska, G. H. Wailes found forms 

 which he considers within this genus, probably P, parimm. Thus 

 far this is the only record of the genus in North America. 



Fig. 323. Platoum parvum. 

 X 725. (After Penard.) 



103 (22) 



104 (107) 



los (106) 



Pseudopodia delicate, filiform, usually branched, and pointed. 



Family Euglyphidae . . 



Pamphagus BaUey 



104 



Pamphagus hyalinus Ehrenberg 1838. 



The aperture of the shell is very large and capable of great 

 dilation. Protoplasm is clear, colorless. Nucleus spherical; 

 contractile vacuole single. Pseudopodia numerous, straight, and 

 pointed. Found in clear water. Diameter of shell 30 to 48 ;». 



Shell flexible, transparent. 

 Shell spherical. 



Fig. 324. Pamphagus hyalinus. cv, contractile vacuole. 

 (After Leidy.) 



X 260. 



106 (105) Shell ovoid or elongate. 



Pamphagus mutahilis Bailey 1853. 



Body very changeable in form. Protoplasm enclosing brilUant 

 granules. Nucleus large, spherical. Contractile vacuoles, one or 

 two. Found in clear water. Length of shell 50 to 70 n. 



Fig. 325. Pamphagus mutabilis. X 165. (After Penard.) 



107 (104) Shell rigid io8 



108 (113) Shell retort-shaped „ 109 



