292 



FRESH-WATER BIOLOGY 



174 (173) Identical with Trichodina, except that the chitinous ring is not 

 denticulate Urccolaria Stein. 



175(172) Without a permanent secondary ring of ciha 176 



176 (177) With two rings of stiff, spinous processes. . . Hastatdla Erlanger. 

 Representative species Hastatella radians Erlanger 1890. 



Fig. 536. nastalella radians. mac«, macronucleus. X 500. (.^fter 

 Erlanger.) 



m^n 



177 (176) Without rings of stiff, spinous processes 178 



178 (179) Posterior end elongated, usually attached; peristome slightly de- 

 veloped. Ciliated disk small. . . . Scyphidia Lachmann. 

 Representative species Scyphidia frotnentellii Kent 1S8 2. 



Body truncate anteriorly; stalk-like appendafije 

 longitudinally striated. Length, extended, 80 n. 

 On water snails. 



Fig. 537. Scyphidia fromentellii. ci;, contractile vacuole; n, 

 nucleus. X 2CX3. (After Kent.) 



'^ ^ 



179 (178) Posterior end not elongated; attached or free. Cylindrical when 

 extended. Ciliated disk small. 



Gerda Claparede and Lachmann. 

 Representative species Gerda sigmoides Kellicott 1885. 



Anterior region narrowed, usually curved. Surface finely striated trans- 

 versely. Nucleus not observed. Length, extended, 150 m- Adherent to 

 fresh-water plants. 



Fig. 538. Gerda sigmoides. x 160. (After Kellicott.) 



180(171) With a stalk. : 181 



181 (186) Stalk unbranched 182 



