OF THE FAMILY BACILLARIA. 145 



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

 D-reat spherical sexual glands 5 s, and the lamelliform extensions 

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

 a, a, a, a, four movement openings, p the pediform organs of 

 motion. 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 

 obtuse on the other, thirteen to fifteen striae in y-^^ of a line, ^l^ to 

 2-1^ of a 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. 



3. Navicida . (PI. IT, fig. 18.) This figure represents a 



panduriform species, very much contracted in the middle. It occurs 

 in peat from a salt marsh near Stonington, Conn. 



4. Navicida . (PI. II, fig. 19.) This species occurs with the 



last, and is perhaps a state of it resulting from its complete sponta- 

 neous division into two individuals by the contraction at the middle. 



5. Navicula . (PI. II, fig. 20.) This resembles the preceding 



very much, but is a fresh-water species, occurring in ponds near 

 West Point ; also in streams in Virginia. 



6. Navicula? striatula. (PI. II, fig. 21, a, b.) I refer to this genus, 

 with much hesitation, the very elegant and interesting species shown 

 by fig. 21 a, h. It is easily known by a set of peculiar and beautiful 

 undulating ridges, represented in the figure, and which give to the 

 margin of the form a rutfled appearance, in whatever position they 

 are observed. One of the faces (a) is lanceolate, the other (b) is 

 somewhat wedgeform, with both ends obtusely truncate. The lan- 

 ceolate face shows a set of fine fines apparently proceeding from the 

 ridges above referred to, and reaching nearly to the middle line of 

 the face. I have sometimes seen two individuals united laterally 

 by their lanceolate faces, producing a very beautiful form. All the 

 individuals which I have seen, have been free, without pedicel, and 

 when living, their spontaneous motions were very distinct. I have 

 found it in a living state in fresh-water ponds and streams near West 

 Point, also in Mountain Run, near Culpepper Court House, in 



