FRESH-WATER BIOLOGY 



141 (142) 



Plates distinct, large size. . . . Trinema enchelys Ehrenberg 1836. 

 The aperture is circular in this species and surrounded by a num- 

 ber of rows of very minute chitinous plates. Pseudopodia very fine 

 and long, usually few in number. This is the most common species 

 of the genus and is found everywhere among mosses. Length 40 to 



IOO p. 



FIG. 342. Trinema enchelys. X 310. (After Penard.) 



142 (141) Plates indistinct, small size. 



Trinema linear e Penard 1890. 



The plates of this small form are indistinct except about the edges, 

 where they may appear as minute undulations. The aperture is round. 

 Habitat as other species. Length 16 to 26 /*. 



FIG. 343. Trinema lineare. X 500. (After Penard.) 



143 (138) Shell shaped as Trinema; aperture subterminal; plates elongate. 



Corythion Taranek. 



Representative species Corythion dubium Taranek 1882. 



In this species the shape of the aperture is characteristic, its border rep- 

 resenting two unequal arcs placed together, the anterior one the longer. 

 The plates are close together but not overlapping. Habitat mosses. 

 Length 35 to 40 /*. 



FIG. 344. Corythion dubium. X 375. (After Penard.) 



144 (2) Pseudopodia usually anastomosing 145 



145 (158) Pseudopodia very delicate, usually finely branched. 



Subclass Foraminifera . . 146 



146 (147) Body without a covering; pseudopodia formed from any part of 



the surface Biomyxa Leidy. 



Representative species Biomyxa vagans Leidy 1875. 



The body moves slowly but continuously, no distinction 

 between ectoplasm and endoplasm being observed. Pseu- 

 dopodia long, branching and anastomosing, always chang- 

 ing. A granular nucleus and a number of contractile 

 vacuoles are present. Habitat sphagnous swamps. Large 

 individuals may measure 480 /* between the tips of the 

 pseudopodia. 



FIG. 345. Biomyxa vagans. X 65. (After Penard.) 



147(146) Body with a distinct covering v- J 4 8 



148(153) Pseudopodia extending from more than one aperture. ... 149 



149 (152) Envelop elongate, compressed. . . Amphitrema Archer . . 150 



150 (151) Envelop transparent, with no foreign particles attached. 



A mphitrema flavum Archer 1878. 



Pseudopodia straight, unbranched, extending from the opposite 

 poles of the envelop. Protoplasm always enclosing chlorophyl. 

 Nucleus single. One or more contractile vacuoles. Habitat 

 mosses. Length 45 to 55 /*. 



FIG. 346. Amphitrema flavum. X 255. (After Penard.) 



151 (150) Envelop with foreign particles attached. ' 



Amphitrema wrightianum Archer 1870. 



In this species the apertures at opposite poles are sur- 

 rounded by short collars. Chlorophyl always present. 

 Pseudopodia often branched. Nucleus single. Contractile 

 vacuoles one or more. Habitat mosses. Length 65 to 70 M- 



FIG. 347. Amphitrema wrightianum. X 215. (After Penard.) 



