CLOSTEKIUM. 47 



0. DIAIO-:, Ehrb. Plate VIII, figs. 8 r 9. Plate IX, fig. 4. 



Plate VI, figs. 1, 2. 



Crescent shape, sometimes a full semi-circle as variety 

 arcuatum, Breb., attenuated from the middle to the rather 

 sharp ends, vacuole not definitely defined ; transverse striae 

 sometimes evident. Ends are separated by about 10 diam- 

 eters. Specimens Plate LV differing somewhat in size. Not 

 rare. Zygospores spherical, smooth. 

 Diameter 16-20 //. 



Quiet waters, Rhode Island to Florida. 



C. ACUMINATUM, Kg. Plate VIII, figs. 18, 19. 



Similar to Diance, somewhat larger and less curved, ends- 

 sharper, vacuoles more distinct; membrane very finely 

 striate, or smooth. 



Diameter 25-28 //. 



Not rare in marsh pools ; conjugated cells frequent. 

 Pennsylvania. 



C. JENNERI, Ealfs. Plate VIII, tig. 5. 



Crescent shaped, small, slightly tapering, six to eight 

 times longer than broad, ends obtusely rounded ; vacuole 

 large, containing many active granules; cytioderm color- 

 less, smooth. 



Diameter about 14 yu. 



Rhode Island (Bailey) ; Pennsylvania, Xew Jersey. 



C. VENUS, Kg. Plate VIII, fig. 6. 



Small, more or less slender, nearly semi-circular, eight to 

 twelve times longer than the diameter ; gradually tapering 

 from the middle to the sharp ends ; vacuole distinct ; cytio- 

 derm colorless and smooth ; chlorophyl homogeneous. 



Diameter 8-10 /^. 



South Carolina, (Ravenel); Pennsylvania, New Jersey, 

 frequent. 



C. PARVULUM, Naeg. Plate VIII, fig. 7 ; and Plate IX, fig. 16. 

 Six to eight times as long as wide ; differs from C. Venu& 

 in being rather less arched and stouter, vacuoles not so welL 

 defined, and chlorophyl lamina more evident. 

 Diameter 12 j. 



