HOLOTRICHA 555 



twisted in dorsal view, due to a spiral depression that runs ob- 

 liquely down toward cytostome; with about 8 caudal setae; in 

 salt water; Florida. 



Genus Homalogastra Kahl. Broad fusiform; furrows spiral to 

 left; a long caudal seta; a group of cilia on right and left sides of 

 it; macronucleus spherical, anterior; contractile vacuole posterior; 

 in fresh water. 



H. setosa K. (Fig. 252, h). About 30^ long; fresh water. 



Genus Stokesia Wenrich. Oblique cone with rounded angles; 

 flat anterior surface uniformly ciliated; mth peristome bearing 

 zones of longer cilia, at the bottom of which is located the cyto- 

 stome; a girdle of longer cilia around the organism in the region 

 of its greatest diameter; pellicle finely striated; with zoochlorel- 

 lae; trichocysts; free-swimming; in freshwater pond. One species. 



S. vernalis W. (Fig. 252, i, j). 100-1 60^ in diameter; macronu- 

 cleus ; 2-4 micronuclei ; fresh water. 



Family 2 Ophryoglenidae Kent 



Genus Ophryoglena Ehrenberg. Ellipsoidal to cylindrical; ends 

 rounded or attenuated; preoral depression in form of '6' due to an 

 ectoplasmic membrane extending from the left edge, cilia on the 

 right edge; cytostome deep-seated; 1 (or 2) contractile vacuole 

 with long radiating canals, opens through pores on right ventral 

 side; macronucleus of various forms \\ith several endosomes; a 

 micronucleus ; fresh or salt water or parasitic. Many species. 



0. collini Lichtenstein (Fig. 252, k). Pyriform; macronucleus 

 horseshoe-shape; 200-300^ by 120-230^t; in the caecum of Baetis 

 larvae. 



0. ^parasitica Andre. Ovoid; dark; micronucleus (?); 170-350^ 

 by 180-200yu; in 'intestine' of Dendrocoelutn lacteum. 



0. pyriformis Rossolimo (Fig. 252, I). Flask-shape; 240-300m 

 long; in intestinal caeca of various Turbellaria. 



0. intestinalis R. (Fig. 252, m). Up to 1.5 mm. by 450-500/^; 

 smallest 60ju long; in the main intestinal canal of Dicotylus sp. 



Family 3 Pleuronematidae Kent 



Genus Pleuronema Dujardin, Ovoid to ellipsoid; peristome be- 

 gins at anterior end and extends for 2/3 the body length ; a con- 

 spicuous membrane at both edges; semicircular swelling to left 

 near oral area; no cytopharynx; close striation longitudinal; 1 to 



