OF THE FAMILY BACILLARIA. 133 



then crushing the specimen under the compressor, starch globules 

 may easily be detected. In crushing, the globules are often 

 forced out at the terminal openings, and on relieving the pressure 

 are drawn back again. No rupture of a membrane at these points 

 was perceived. 



4. Closteriurii digitus. (Fig. 33 ? PI. I.) Straight, oval, cylindri- 

 cal, four or five times longer than broad, smooth, the ends very much 

 romided, sometimes showing traces of a spontaneous triple division, 

 longitudinal bands often denticulate, one twentieth to one tenth of 

 a line. «, 



With this account may be compared fig. 33, PI. I, which rep- 

 resents a species not uncommon at West Point, and which I 

 have also seen in Rhode Island, Virginia, and Ouisconsin. 



Its endochrome usually presents a central mass, from which 

 several (10 ?) undulating ridges radiate to the carapace. It is a 

 very elegant species. 



5. Closterium lincatum. (Fig. 34 ? PI. I.) Very long, acute, slightly 

 arcuate, cylindrical, filiform in the middle, the ends truncate, and very 

 attenuate, (" tres amincis") ridges distinct, inform of smooth lines. 

 Often thirty times longer than broad, one eighteenth to one eighth of 

 a line. 



Compare with this fig. 34, PI. I, which represents a species 

 quite common in ponds near West Point, and which also occurs 

 in Virginia. The figure represents only one half of the exces- 

 sively elongated body. In the living specimens, the endochrome 

 shows distinct ridges. 



6. Closterium striolatum. (Fig. 3-5? PL I.) Fusiform and arcuate, 

 ends acute and truncate, ridges smooth, not deep, ten or twelve 

 times longer than broad, one tenth of a line. 



Compare fig. 35, PI. I, which represents a common species. 



7. Closterium rostratum, Ehr. Fusiform, slender, ends acute, seta- 

 ceous horns about as long as the body, sometimes shorter. C acus, 

 Ktz. Linn., 1833. fig. 81. 



I suspect the species shown in fig. 36, PI. I, is a young state 

 of this species. I found it among Lemna minor, on Staten 

 Island, New York. Fig. 36, o, shows an individual produced 

 by spontaneous division, one portion of which is still imperfectly 

 developed. 



