PERITRICHA 619 



holds fast to gill bars of the mussel, Donax vittatus. One spe- 

 cies. 



E. donacis C. et L. (Fig. 280, h). 50/z by 40^1, excluding the 

 processes. 



Family 4 Epistylidae Kent 



Genus Epistylis Ehrenberg. Inverted bell-form; usually indi- 

 viduals on dichotomous non-contractile stalk, forming large 

 colonies; attached to fresh or salt water animals. Numerous 

 species. 



E. plicatilis E. (Fig. 280, c). OO-IOOaj long; colony often up to 

 3 mm. in height; fresh water. 



E. fugitans Kellicott (Fig. 280, d). 50-60/i long; attached to 

 Sida in early spring; Niagara river, N. Y. 



E. cambari K. (Fig. 280, e,f). About 50/x long; attached to gills 

 of Cambarus; Niagara river, N. Y. 



Genus Rhabdostyla Kent. Similar to Epistylis; but solitary 

 with a non-contractile stalk; attached to aquatic animals in 

 fresh or salt water. Numerous species. 



R. vernalis Stokes (Fig. 280, g). About 50/^ long; attached to 

 Cyclops and Cypris in pools in early spring. 



Genus Opisthostyla Stokes. Similar to Rhabdostyla; but stalk 

 long and bent at its point of attachment to submerged object, 

 and acts like a spring; fresh or salt water. 



0. annulata S. (Fig. 280, h). Body about 23/x long; fresh water. 



Genus Campanella Goldfuss. Similar to Epistylis; but adoral 

 double zone turns 4-6 times; fresh water. 



C. umhellaria (Linnaeus) (Fig. 280, i). Colony may reach 

 several millimeters in height; individuals 130-350ai long (Kent). 



Genus Pyxidium Kent. Stalk simple, not branching; peristome 

 even when fully opened, not constricted from the body proper; 

 frontal disk small, oblique, supported by style-like slender 

 process arising from peristome; attached to freshwater animals 

 and in vegetation. 



P. vernale Stokes (Fig. 280, j). Solitary or few together; 70-85/: 

 long; fresh water among algae. 



P. urceolatum S. (Fig. 280, k). About 90/: long; fresh water on 

 plants. 



Genus Opercularia Stein. Individuals similar to Pyxidium; 

 but short stalk dichotomous; peristome border like a band. 



