322 Sketch of the Infusoria of the family Bacillaria. 



tests. A good idea of the general form of this genus may be got 

 from Plate 4, fig. 153, of Pritchard's Infusoria. 



Synedra. 



Carapace simple, siliceous, fixed when young by one extremity, 

 when older often free, longer than broad, foot either wanting or 

 rudimentary, form elongated or prismatic. 



Synedra ? (PI. 3, fig. 1.)* Frustules long, slender, linear, 



adhering laterally into plates which are supported by a short fleshy 

 pedicel, and terminated by a fleshy mass. 



The species whose usual appearance is shown in PI. 3, fig. 1, 

 occurs in vast quantities on various Algae in the Hudson River at 

 West Point. It usually completely envelopes the plants to which 

 it is attached, giving them a covering of bristling crystal-like par- 

 ticles, through which it is often difficult to see any portion of the 

 supporting plant. When the Algse on which it grows are dried, 

 they often have a greenish gray hue, from the presence of this 

 parasite. 



It presents considerable resemblance to S. Gailloni, Ehr. (Dia- 

 toma crystallinum, Ag.) and has, like that, minute striae on the 

 edges, but I have seen no allusion made in the descriptions of 

 that species to the fleshy projection which is so conspicuous in 

 our species. 



A person who sees how abundant this species is in the recent 

 state, will no longer wonder that in the lapse of years masses 

 of infusorial shells should accumulate so as to form extensive 

 strata. 



Synedra ? (PI. 3, fig. 2.) Frustules linear, strait, striate, 



truncate on the lateral side, ventral sides with a neck-like contraction 

 near each end, ends rounded. 



This species is very abundant in fresh water near West Point, 

 often covering aquatic plants with a glittering envelope of crystal- 

 like frustules. The individuals are perfectly linear with truncate 

 ends. When seen laterally, they show near their extremities a 

 slight contraction, which forms a neck supporting the round or 

 knob-like terminations. Minute striae may be seen as represent- 

 ed in the figure. 



* Plate III, which accompanies this part of Prof. Bailey's article, is also marked 

 V in the series of plates contained in the present volume of this Journal. Plate 

 III is marked at the bottom and plate V at the top of the plate.— Eds. 



