Sketch of the Infusoria of the family Bacillaria. 101 



COCCONEIS. 



Free, single, carapace simple, bivalve (siliceous) prismatic or 

 hemispherical, a single opening in the middle of both sides of 

 each carapace {?), never double or catenate by spontaneous di- 

 vision. 



1. Cocconeis 7 (PI. 2, fig. 34.) Represents what I believe to be a 

 species of Cocconeis. I found it adhering to a small marine Alga from 

 the eastern shore of Florida. 



Beautiful figures of Cocconeis {Cam,pylodiscus) clypeus, drawn 

 by F. Bauer, will be found in Pritchard's Hist. Inf., PI. 12, fig. 

 516 — 518. I have received fine specimens of these elegant fos- 

 sils from E. J. Gluekett, Esq., of London. 



Bacillaria. 



Pree, {never fixed) carapace simple, bivalve or mitliivalve (sili- 

 ceous) prismatic, formiiig chaijis or zigzag polypidom,s by im- 

 perfect spontaneous division of the carapace and perfect division 

 of the body. 



1. Bacillaria paradoxa. (PI. 2, fig. 35.) — The standard bearer. — 

 Striate, carapace linear, very slender, often fifteen times longer than 

 broad, yellow, frustules very active, -^^ to ^V li^^e- Syn. Vibrio pax- 

 iUifer, MMer. See Encyl. Meth. PI. 3, fig. 16 to 20. 



I first detected this species in October, 1840, among Algse 

 from the Hudson River, near West Point. I am informed by 

 Dr. P. B. Goddard of Philadelphia, that it also occurs in abund- 

 ance near that city. It is a very interesting species, presenting 

 by its curious motions and paradoxical appearance, an object well 

 calculated to astonish all who behold it. At one moment, the 

 needle-shaped frustules lie side by side, forming a rectangular 

 plate ; suddenly, one of the frustules slides forward a little ways, 

 the next slides a little also, and so on through the whole number, 

 each however retaining a contact through part of its length with 

 the adjoining ones. By this united motion the parallelogram is 

 changed into a long line ; then some of the frustules slide together 

 again, so that the form is then much like a standard. Similar 

 motions are constantly going on, and with such rapidity that the 

 eye can scarcely follow them. There are few more interesting 

 objects for the microscope. 



Several of the positions of these singular productions are well 

 represented by Miiller. (See Enc. Mcth. Vers. PI. fig. 16 — 20.) 



