12 MICROSCOPICAL O li S K K V A T I () NS. 



5. PTERODINA MAGNA, B. On St. Anastasia Island, in a small fresh-water poiul, 

 I collected a species of Pterodina with a carapace nearly twice as large as any 

 specimens of P. patina which I have ever seen, and differing somewhat in the 

 undulations of its frontal margin. Although it has not yet been sufficiently 

 studied to be accurately described, I give its outline in PI. 3, fig H, and have 

 referred to it by the name of P. magna. 



6. PHILODINA PANNOSA, B. PI. 3, figs. 6, 7. Body large, covered with irregular 

 wedge-shaped projections, arranged in several longitudinal and transverse rows. 



Hab. Enterprise, Fa. 



ALGJE. 



1. APOREA AMBIGUA, B. PI. 3, fig. 3. Frond (?) microscopical, thin, flat, much 

 divided in a dichotomous manner, surface with irregular longitudinal markings ; 

 color, brown. 



Merely to avoid circumlocution, I have referred by the above name to this 

 constantly occurring form. I know nothing of its real nature ; and it is almost 

 as probable that it is the compound support of some of the stipitate infusoria, as 

 that it belongs to the vegetable kingdom. I have never seen either spores or 

 infusoria in connection with it. It occurs everywhere in fresh water in Georgia 

 and Florida. 



GENERAL REMARKS. 



1. It will be seen by the preceding pages, that 275 species of Desmidiete, 

 Diatomacese, and Infusoria have been positively determined as occurring in 

 regions where not one of them was previously known by direct observation to 

 exist. Of these species, thirty-one, or about one-ninth, are believed to be new r , 

 and the others are already known to occur in the Northern States, or in Europe. 



2. The identity of many of the northern species of Desmidiese, &c., with those 

 of Europe, has been known for several years, and we now have evidence that 

 the same is true with regard to the greater number of the forms occurring in 

 Carolina, Georgia, and Florida. We have thus another illustration of the fact, 

 that the microscopical organisms in fresh water are less affected by differences 

 of climate than almost any other portion of the organic world. 



3. Almost every locality examined, whether in fresh or salt water, is shown 

 to have been teeming with organic life even in mid-winter. 



4. With regard to the degree of reliance to be placed upon my determinations, 

 I may state, that no one could have criticised each observation more rigidly than 

 I have done, and that I was anxious to admit no species into my lists which I 

 could not be perfectly certain was identical with the European or Northern 

 form whose name I might attach to it, while I was equally desirous to record all 

 forms which appeared novel, and which presented characters sufficiently marked 

 to enable other observers to recognize them by my description and figures. I 



