422 OHIO BIOLOGICAL SURVEY 



2. P. marina n. sp. (Fig. 2, PI. XXVI) . 



Fusiform, rigid, not compressed; 8 longitudinal carinae 

 slightly spiral; cell transparent; primary flagellum 2/3 length of 

 body; secondary flagellum 2 times length of body. 



L. 50^. D. 2Six. 



Distribution, cosmopolitan. Two species. 

 Woods Holl, Mass. 



This form was described and illustrated in a well drawn figure 

 by Calkins (U. S. Fish Com. Bull., p. 426, 1901— printed 1902) 

 under the name Anisonema vitrea Duj., a species which belongs 

 to the genus Ploeotia. It differs from P. vitrea by the characters 

 noted above. The length of its secondary flagellum eliminates it 

 from the genus Tropidoscmyhus, while the presence of keel-like 

 ribs or carinae removes it from the genus Anisonema. The genus 

 Ploetia is founded on a form laterally compressed. It seems bet- 

 ter, however, to remove such a qualification and place it here 

 rather than make a new genus for its reception. 



11. Gen. METANEMA Klebs. 



Form oval, metabolic comparatively short, compressed dorso- 

 ventrally; two flagella of approximately equal length, the poste- 

 rior, however, not trailing directly behind, but carried to one side 

 during swimming. 



Habitat, fresh water. 



Distribution, cosmopolitan. Two species. 



TABLE OF SPECIES. 



Ai Pellicula smooth . . . . . . . 1. M. variabile 



A2 Pellicula with distinct spiral striae . . . . 2. M. striatum 



1. M. variabile Klebs (Fig. 3, PI. XXVI). 



Short cylindrical, decidedly metabolic, rounded on ends ; peri- 

 plast smooth ; primary flagellum as long as body ; secondary flagel- 

 lum somewhat longer than body. 



L. 14-16/x. D. 9-12/x. 



Distribution, Europe. Standing water. 



2. M. striatum Klebs (Fig. 4, PI. XXVI). 



Cylindrical, slightly metabolic, flattened, emarginate ante- 

 riorly ; periplast spirally striate ; primary flagellum slightly longer 



