1687.] PROCEEDINGS OF UNITED STATES XATIOXAL MUSEUM. 357 



Plorida; but the same is almost equally true with respect to the mode 

 of growth, although davaria is usually a much stouter foriu thau/«r- 

 cata. lu both species the columeUa may be present or lackiug eveu in 

 the same specimen, but, as a rule, the center of the cell is seldom deeply 

 joerforated, aud the free portion of the columelhi is much more sleuder 

 and less conspicuous than the pali, which are generally well developed. 

 Constant reliance cannot be placed upon the relative compactness of 

 the texture, either internally or externally, but it is generally somewhat 

 looser in furcata, the cells rather smaller, irregular, polygonal, sepa- 

 rated by thin walls ; while in davaria the walls Are often much thick- 

 ened, porous, the septa sometimes, but not always, better developed, 

 the excavated portion of the cell almost always circular in outline and. 

 legular. The cells may be superficial to moderately deep in both species, 

 but become most excavated at times in davaria ; the echinulation varies 

 similarly in both, but the processes are very rarely nearly smooth in 

 either, and when so are much twisted and very irregular. The figures of 

 the cells of furcata and davaria given in " The Memoirs of the Museum 

 of Comparative Zoology," vol. vii, 1880, pi. xii, fig. 5, pi. xvi, fig. 14, 

 might serve indiflerentlj" for either species, but those on pi. xii, fig. 5, 

 labeled davaria, are of rare occurrence in our collection. 



In classifying the collection in the National Museum, the writer has 

 followed as closely as possible the views of Dana, Verrill, an d Pourtales, 

 relying for his data upon specimens in the old collection labeled by Dana 

 and Verrill, and upon the few brief diagnoses that have been published. 

 There is no difiBculty in assigning most of the specimens to one or other 

 of the two species, which appear very distinct in what may be called 

 their typical forms, but there exist a large number of intermediate varie- 

 ties the exact position of which cannot bo determined, aud which render 

 the specific value of the two forms somewhat doubtful. The depth at 

 which they grow aud the nature of their surroundings undoubtedly have 

 much to do with the character of their growth, but many of the varia- 

 tions cannot be explained by such means. It is to be regretted that 

 fuller notes are not made by collectors in the field upon the conditions 

 attending the growth of such forms as these, for they would probably 

 serve to show relationships which might not otherwise be suspected. 

 Fortunately, in the last and largest collection received from Florida 

 all the specimens from each locality have been kept together, and it is 

 shown that each spot hasits peculiar variety or varieties, differing more 

 or less from those of all the others. 



In the specimens referred to furcata, the tendency is to form small, 

 more or less dense, clumps, composed of rather slender, rapidly dividing 

 branches, with relatively small, crowded, polygonal aud often very 

 irregular cells, vseparated by thin walls, and either superficial or moder- 

 ately excavated. In davaria, which is more varied in growth, the 

 branches, on the contrary, are generally stout, dividing much less 

 rapidly and forming open clumps or very short, rapidly tapering and 



