40 MICROSCOPICAL OBSERVATIONS. 



The outline is like that of P. paradoxa, Ehr., and the markings somewhat 

 resemble those of P. lyra. 



Hab. St. Augustine. 



I take great pleasure in dedicating it to James Hamilton Couper, Esq., of 

 Hopeton, whose scientific attainments and generous hospitality are well known 

 to naturalists. 



11. PINNULARIA PERMAGNA, B. PI. 2, figs. 28 and 38. Large, lanceolate on the 

 ventral faces, with punctato-striate marginal bands, and a broad, smooth central 

 stripe ; ends slightly rounded. 



Abundant in the Hudson River, at West Point, and occurs, of a smaller size, 

 and much less abundantly, in Lake Monroe, at Enterprise, Fa. 



12. PYXIDICULA ? COMPRESSA, B. PI. 2, figs. 13 and 14. Elliptical, bivalve; 

 valves separated by a plane passing through the longer axis ; slightly convex, 

 and with transverse rows of dots. 



Hab. St. Augustine. 



13. STAURONEIS MACULATA, B. PI. 2, fig. 32. Lanceolate or elliptical, end 

 slightly produced and rounded ; surface punctato-striate, with a large smooth 

 central space. 



Resembles S. punctata of Kiitzing's Bacillarien, PI. 21, fig. 9, but is larger, 

 and has the ends not so much produced. 



Hab. Enterprise, Florida, where it is common in Lake Monroe, and in several 

 of the smaller creeks near Mr. Duval's. 



14. SURIRELLA CIRCUMSUTA, B. PI. 2, fig. 36. Outline nearly elliptical, with a 

 scarcely perceptible constriction at the middle. Surface with very minute 

 granulations, and a faint longitudinal line through the middle. Edges with a 

 continuous row of nearly obsolete pinnule. 



Hab. Hudson River, West Point ; St. Augustine and Enterprise, Florida. 



15. TRICERATIUM ALTERNANS, B. Small, reticulated, triangular; surface 

 marked with three lines, which, with the portions cut off from the sides, form 

 a hexagonal figure. 



Common everywhere along the Atlantic coast and in estuaries ; also abundant 

 in the fossil state, in the Infusorial strata of Virginia, and in the rice fields of 

 Georgia and Carolina. 



16. ZYGOZEROS (DENTICELLA?) MOBILIENSIS, B. PI. 2, figs. 34 and 35. Frustules 

 quadrangular, compressed, thin, delicately decussatedly-punctate ; lateral pro- 

 cesses slender; intermediate ones (two at each end) long and slender. Color 

 yellowish. 



