66 GEOLOGY OF THE FIRST DISTRICT. 
PyxiDictJLA. Free, carapace simple, bivalve [siliceous) separate, globular; [may be compared to a 
Gaillonella with perfect spontaneous division or without division.) 
Pyxidicula operculata. (PI. 22, fig. I and 1 a.) Body spherical, divisible into two hemispheres, cara¬ 
pace hyaline, internal organs greenish yellow, yip to Jy line. 
I have seen hemispheres, probably derived from this species, among fossil infusoria from 
Manchester, Mass. &c. 
Pyxidicula globata. This name has been given to globular bodies found in flint. Beautiful figures of 
them by Bauer, will be found in Pritchard’s Hist. Infusoria, pi. 12, figs. 506 to 509. It is now 
suspected that these bodies are the gemmules of sponges, as the ramified tubes of sponge are often 
found preserved in the same pieces of flint. 
Pyxidicula ? (PI. 22, fig. 2, a, b.) The spheroidal bodies represented by these figures, occur in the 
tertiary infusorial stratum discovered by Prof W. B. Rogers in Virginia.* Of the real nature of 
these bodies I am quite uncertain; they agree however with Pyxidicula, in separating into two 
hemispherical portions. The surface is beautifully marked with rows of circular or hexagonal 
spots or cells, resembling those on the beautiful species of Coscinodiscus which accompany these 
bodies in the same deposit. ' 
Gaillonella. Free, carapace simple, bivalve [siliceous); form cylindrical, globular or discoid, 
producing chains [long articulated cylinders) by imperfect spontaneous division. 
Gaillonella moniliformis. (PI. 2, fig. 3.) Corpuscles smooth, cylindrical, short, conical at the sides 
and truncate, form octangular [?] circular when seen endwise, ovaries green, y’y line. Ehr. 
Meloseira moniliformis, Ktz. (Linn., 1833, PI. 17, fig. 71.) M. nummuloides, Grev. (in Brit. 
Flora, Vol. 5, p. 401.) 
This very beautiful species grows only in salt or brackish water, and occurs in great abun¬ 
dance in various places in the United States, I first noticed it several years ago, among spe¬ 
cimens of algae from Providence, R. I. I subsequently found it almost covering the bottom 
and shores of Providence cove at low tide. I found it again in vast quantities, in salt ditches 
near the railroad at Stonington, Conn., where it formed large fleecy masses, sometimes of 
several feet in extent. Still more recently I have found it at Staten Island, and also, much to 
my surprise, sixty miles up the Hudson river near West-Point.t 
The form is not strictly octangular, but at first appears so, in consequence of the two 
♦ For an account of this truly interesting discovery, see Report on Geology of Virginia for 1840. The infusorial strata of 
Virginia are of great interest from their vast extent, and from being the first infusorial deposits noticed in this country, of a period 
anterior to the present epoch. I am indebted to Prof. Rogers for specimens from various localities, and with his permission I include 
in this article figures drawn by myself of several of the interesting forms found in these beds. 
t The Flora and Fauna of the Hudson river at West-Point would, in a fossil state, be rather puzzling to the geologist, on ac¬ 
count of the singular mixture of marine and fluviatile species. While Vallisneria and Potamogeton grow in such vast quantities 
in many places as to prevent the passage of a boat, and the shore is covered with fluviatile shells, such as Planorbis, Physa, &c. 
in a living state ; we yet find the above fresh-water plants entangled with bunches of marine alg®, such as Enteromorpha, Ecto- 
carpus, &c., and often covered with marine parasitic zoophytes and marine infusoria (Achnanthes, Gaillonella, Echinella, 
Naunema, &c.; while the rocks below low water mark are covered with Balani and minute corallines, and the marine flora is 
represented by vast quantities of a very elegant Polysiphonia, nov. sp. ?) abundance of Enteromorpha intestinalis, Ectocarpus 
siliculosus. and an elegant Alga, apparently identical with Delesseria leprieurii of Montagne, which was first detected on the 
shores of Cayenne. (See Annales des Sciences Naturelles, 2d series, Bot., tom. 13, p. 196, and pi. 5. 
