Common in the plankton of hard water lakes. Frequently found 

 with p. sociale. Sometimes the most conspicuous element in the 

 phytoplankton. Mich., Wis. 



Dinobryon sertularia var. protuberans 

 (Lemm.) Krieger 1930, p. 308 



Loricas 24-35.5/i, long; basal portion with unsymmetrical swellings. 

 Euplankter. Wis. 



Dinobryon sociale Ehenberg 1835, p. 279 

 [D. stipitatum Stein] 



PI. 98, Fig. 13 



Colonies loosely branched, slightly spreading. Loricas cone- 

 shaped, either straight or bent, blunt-pointed posteriorly, the 

 lateral margins smooth and usually diverging symmetrically to the 

 wide, slightly flaring mouth; 7— 8/j, in diameter, 30— 70/i, long. 



Common in the plankton of hard water lakes; generally distri- 

 buted. Mich., Wis. 



Dinobryon sociale var. americanwn (Brunn.) 

 Bachmann 1911, p. 54 



A variety with relatively shorter and wdder loricas; the mouth 

 flaring slightly; subcylindrical above, narrowing abruptly posteriorly 

 to a sharply pointed cone which is about one-half the length of the 

 cell; 21-38jLi long. 



Euplankter. Wis. 



Dinobryon Tabellariae (Lemm.) Pascher in 

 Pascher & Lemmermann 1913, p. 66 



PI. 98, Figs. 3-5 



Solitary, epiphytic on the diatom Tabellaria. Loricas broadly fusi- 

 form, extended posteriorly into a short tapering stipe; 7-lOju, in 

 diameter, 18-22;u, long. 



Plankter; in a variety of lakes. Wis. 



Dinobryon Vanhoeffenii ( Krieg. ) Bachmann 1921 



ex Ahlstrom 1937, p. 157 



[D. stipitatum var. affine Taylor 1935, p. 88] 



PI. 107, Fig. 14 

 Loricas in diverging colonies, mouth of the lorica straight or 

 flaring almost imperceptibly, subcylindrical above, with undulate 

 margins, gradually and symmetrically narrowed posteriorly to a 



[379] 



