Sketch of the Infusoria of the family Bacillaria. 97 



is equally diffused in this country. I have myself observed it in 

 Maine, Massachusetts, New York. Ouisconsin and Virginia. It 

 is easily recognized by means of its large size and beautifully 

 marked ventral faces. The striae seen on these faces may cor- 

 respond to internal cells, but I believe them to be linear openings 

 in the carapace itself, as may easily be seen on the fragments of 

 fossil specimens. There are three rounded spaces on each ven- 

 tral face, which I think have been mistaken for openings, but 

 which appear to me to be thicker portions of the carapace. One 

 of these spaces is in the middle, and the other two at the extrem- 

 ities of the striated surfaces, and they are connected by a very 

 delicate double line (canal ?) A similar structure is seen on sev- 

 eral other species of Navicula, Cocconema and Gomphonema. 

 The real orifices are shown at c, c, c, c, in our fig. 16, b. Moving 

 particles somewhat like those of Closterium may sometimes be 

 seen near the extremities. In fig. 17, a, b. Pi. 2, I have copied 

 from Ehrenberg, (Die Fossilen Infusorien und die lebendige Dam- 

 merde, Berlin, 1837, PI. 1, fig. 19,) a sketch in which he repre- 

 sents the organs of motion, the stomach &c. of this species. The 

 reference letters having been omitted by the engraver of Ehren- 

 berg's plate, I have been obliged to insert them according to what 

 I believe was their intended position. 



The following is a translation of Ehrenberg's explanation of 

 this figure. (See fig. 17, PI. — .) 



"A living specimen of Navicula viridis, in which by the injec- 

 tion of indigo are distinctly to be seen ; the stomach v, the two 

 great spherical sexual glands s s, and the lamelliform extensions 

 of the green ovarium, o' mouth opening, o' sexual opening? 

 a, a, a. a, four movement openings, j9 the pediforra organs of mo- 

 tion. The visible currents on the body, both when creeping and 

 at rest, are denoted by arrows." 



2. Navicula viridula. Carapace straight, lanceolate, linear, very 

 slender, truncate at the ends, flattened on one side, lanceolate and ob- 

 tuse on the other, 13 to 15 stria? in -jiiy lii^e, v-^^er to —• line. Frustulia 

 viridula, Ktz., Linn. 1833, PI. 13, fig. 12. 



Ehrenberg mentions this as one of the species detected by him 

 among fossil infusoria from West Point. Kutzing's figure does 

 not allow me to determine with certainty, which of the various 

 forms occurring at West Point, belongs to this species. 



Vol. xhu, No. 1.— Oct.-Dec. 1841. 13 



