38 MICROSCOPICAL OBSERVATIONS. 



12. TRIPLOCERAS GRACILE, B. PI. 1, fig. 10. Slender, with whorls of rounded 

 projections. Ralfs, 1. c. Fig. 9, c. 



I discovered these forms in Rhode Island, in 1847, and sent sketches of them 

 to Ralfs, who has published an account of them in his British Desmidiese, p. 219. 

 I then included both forms under the same name, but as I have now seen great 

 numbers of each kind, I think them sufficiently distinct to be separated. 



Hab. Worden's Pond, R. I., Princeton, N. J., Georgia and Florida. Abun- 

 dant in lakes near Enterprise, Fa. 



DIATOMACE^E. 



1. ACIINANTHES ? ARENicoLA, B. PI. 2, fig. 19. Frustules minute, rectangular, 

 or slightly curved ; end view lanceolate, striate. 



Small plates, composed of two or three frustules, supported by a short pedicel, 

 were found abundantly on grains of the beach sand, below high-water mark, at 

 Fort Brooke, Tampa. It is possibly a species of Hyaloseira, but requires further 

 study. 



2. AMPHIPRORA PULCHRA, B. PI. 2, figs 16 and 18. Large, deeply constricted, 

 ends rounded, sides compressed, carinate, distinctly striate, and near the margin 

 punctate. Central portion narrow, sigmoid, with a few fine longitudinal lines. 

 Often contorted so as to bring one half into a plane at right angles to the other. 



Hab. Beach at Rockaway, Long Island ; Hudson River, at Washington's 

 Valley, near West Point, and in great abundance and of large size at Enterprise, 

 Fa. The figures were drawn from Florida specimens collected in the mud of a 

 small creek near Mr. Duval's boarding-house, at Enterprise. 



3. AMPHIPRORA ORNATA, B. PI. 2, figs. 15 and 23. Small, deeply constricted, 

 ends truncated and rounded, sides marked with a longitudinal row of undula- 

 tions or pinnulee, as in Surirella. Often contorted. 



The ruffle-like rows of phmulse distinguish this species from all others. It 

 probably has minute striae also, but I did not have an opportunity to examine 

 with high powers. 



Hab. Withlacoochee River, where it is crossed by the road from Pilatka to 

 Tampa, Fa. 



4. AMPHIPRORA QUADRIFASCIATA, B. PI. 2, figs. 2, 3, 4. Small, moderately 

 constricted, ends truncate or slightly rounded, sides compressed or carinate, 

 lanceolate, with the apices produced and rostellate. 



When living, each specimen was marked by four transverse yellow bands. A 

 high power shows the surface to be very minutely striate. No contorted 

 specimens were seen. 



Hab. Tampa, and St. Augustine, Fa. 



