574 PROTOZOOLOGY 



Peristomal field drawn out into 2 wings; with flask-shaped, 



thin-walled pseudochitinous lorica 



Family 6 Folliculinidae (p. 584) 



Body ciliation either confined to ventral side or lacking 



Free-living; flattened; cilia only on ventral surface; adoral zone sur- 

 rounds anterior region of ventral surface; cytostome on left 



edge near middle of body Family 7 Peritromidae (p. 584) 



Ectocommensal; extremities discoid; body narrowed; anterior disk 

 surrounded spirally by adoral zone; posterior disk bears mem- 

 branous cilia Family 8 Licnophoridae (p. 586) 



Family 1 Bursariidae Perty 



Genus Bursaria Miiller. Ovoid; anterior end truncate, posterior 

 end broadly rounded; dorsal surface convex, ventral surface 

 flattened; deep peristome begins at anterior end and reaches 

 about central part of body, where it gives rise to cytostome and 

 cytopharynx, which is bent to left; lengthwise fold divides peri- 

 stome into 2 chambers; striation longitudinal; ciliation complete 

 and uniform; macronucleus band-form; many micronuclei; many 

 contractile vacuoles distributed along lateral and posterior bor- 

 ders; cysts with a double envelope; fresh water. One species. 



B. truncatella M. (Fig. 261, a). 500-IOOOm long. 



Genus Thylacidium Schewiakoff. Similar to Bursaria in general 

 appearance; but smaller in size, peristome simple in structure 

 without longitudinal fold; with zoochlorellae; fresh water. One 

 species. 



T. truncatum S. (Fig. 261, h). 60-100m long. 



Genus Bursaridium Lauterborn. Similar to Bursaria; peri- 

 stome funnel turns to right , fresh water. 



B. difficile Kahl (Fig. 261, c). Anterior end truncate, slanting 

 toward right; about 130/i long. 



Genus Balantidium Claparede et Lachmann {Balantidiopsis 

 Biitschli; Balantiod aides Alexeieff). Oval, ellipsoid to subcylindri- 

 cal; peristome begins at or near anterior end; cytopharynx not 

 well developed; longitudinal ciliation uniform; macronucleus 

 elongated; a micronucleus; contractile vacuole and cytopyge ter- 

 minal; in gut of vertebrates and invertebrates. Numerous species. 

 Hegner (1934) states that the size and shape of body and macro- 

 nucleus could be made a satisfactory basis for specific identifica- 

 tion. 



B. coli (Malmsten) (Fig. 261, d, e). Ovoid or pyriform; 30 150^ 

 by 25-120/i; oblique peristomal depression below anterior tip; 



