MICROSCOPICAL OBSERVATIONS. 39 



5. Amphora AMPiiioxys, B. PI. 2, figs. 20, 21, 22. Ventral side rectangular, 

 with slightly rounded ends, and two arcuate bands of striae, which are broadest 

 near the centre. Back convex, minutely striate. Sides convex above, minutely 

 striate, concave below_, strongly striate. Ends produced and rostellate. 



The side view of this species bears a striking resemblance to Eunotia 

 amphioxys, Ehr. 



Hab. St. Anastasia Island, near St, Augustine, Fa. 



(3. Campylodiscus ARGUS, B. PI. 2, figs. 24, 25. Large, circular, and saddle- 

 shaped, surface marked with rows of conspicuous dots ; margin smooth, with a 

 row of pinnulae placed at a short distance from its edge. 



A fine, large, and very distinct species, which appears to be widely diffused 

 in the estuaries of the United States. I first found it, several years ago, in the 

 mud of the Hudson River, at West Point, and in mud from the harbor of New 

 Haven, Conn. In Florida I found it at St. Augustine, Tampa, and quite abundant 

 at Enterprise. I also noticed it at Hopeton, on the Altamaha, in Georgia, and 

 the mud from near New Orleans. 



7. Cerataulus turgidus, Ehr. PI. 2, figs. 26, 27, Frustules globular, or 

 slightly compressed, with two large rounded prominences at each end, cohering 

 by alternate angles, forming zigzag chains. BetAveen the two rounded processes, 

 and in a plane at right angles to that containing them, are placed two long horn- 

 like processes. 



Two frustules are often connected by an external decussately punctate cell, 

 as in Isthmia and Biddulphia. I first noticed this species at Rockaway, N. J., 

 in the year 1843, and sent it to Ehrenberg, who informed me that he had named 

 it Cerataulus turgidus. 



I am not aware that any description of it has heretofore been published. 



I found it at Tampa ; and it also occurs in the Hudson River, at West Point. 



8. DiATOMA stellaris, B. Frustules rectangular, many times longer than broad, 

 usually in groups of five or six individuals, cohering by the adjacent (not alter- 

 nate) angles, so as to produce a stellate ari-angement. These stellate groups of 

 minute frustules are so common from Rhode Island to Florida, that I am inclined 

 to believe them a distinct species of Diatoma, and have accordingly referred 

 to them by the name of D. stellaris in the preceding pages. 



9. EupoDiscus RADiATUS, B. In form, size, and reticulation resembling the 

 Coscinodiscus radiatus of Ehrenberg, but having four (or more 1) foot-like pro- 

 jections near the margin. 



A common form in the Southern States. 



10. PiNNULARiA CouPERii, B. PI. 2, fig. 33. Large, slightly constricted in the 

 middle, with two marginal and two intermediate punctato-striate bands, the 

 latter interrupted at the centre. 



