760 REPOET OF COMMISSIONER OF FISH AND FISHERIES. [6] 



of an iucli in diameter, and hence of a sufficient size to be preyed upon 

 by a larger artliropod. The remarkable Pyrocystis noctihica, discovered 

 by Mr. Murray, and nearly a millimeter in diameter, is another inter- 

 esting surface form, as is also the P. fusiformis, which is allied to it> 

 Both are phosphorescent surface swimmers, and fall within the reach of 

 other surface animals as a probable source of food. To these may be 

 added the curious group of the Challengerida, together with the whole 

 of the Badiolaria, with their siliceous shells, which, in the warmer parts 

 of the high seas, actually tinge the surface when some of the highlj-- 

 colored forms are abundant. From the surface of the mi«l-Atlantic the " 

 Challenger crew obtained stalked iufusorians fixed to the shell of Spi- 

 rilla ; also an abundance of large radiolariaus. Haeckel, Monograph of 

 the Radiolaria, says the largest living Eadiolaria measure only a few 

 lines in diameter, but most of them are much smaller, and attain 

 scarcely a tenth down to a twentieth of a line in diameter. At Saint 

 Jerome's Creek, Maryland, in one of its arms which is now used as au 

 oyster i^ark, the writer found an abundance of a fresh-water Heliozoan, 

 not specificially distinguishable from Actinophrys sol. They were found 

 in great abundance at times on the surface of the slate collectors which 

 had been put down for the i^urpose of enabling the free-swimming fry 

 of the oyster to fix itself. This raises the question whether the fresh- 

 water protozoan fauna does not overlap the marine. The water in the 

 situation mentioned was not simj^ly brackish, but positively salt. In the 

 same place great numbers of stalked and tube or test building ciliate . 

 forms of Protozoa were also found. The magnificent bottle-green Freia 

 prodiicta was found in the same locality in the greatest profusion. Some- 

 times several hundred mighthavebeen counted on a single square inch of 

 the surface of oyster shells, slates, or boards, giving such surfaces a dark- 

 greenish or speckled tint from their numbers. Very small species of 

 nudibranchiate mollusks {JEoHs and Doris) were found creeping amongst 

 and over the forest of Protozoa, pasturing oft" of them. Amongst the 

 tubes of the Freia, and attached to them, a small operculate Coilmrniay 

 with a rich brow^u-colored test, was found in abundance, and, rarely, a 

 very curious form of Tintinnus, with a tubular, subulate test, to the 

 inside of which the stalk of the inhabitant was attached, at one side, 

 about half way uj) from its base. The open or mouth end of the per- 

 fectly hyaline test was verj- strongly toothed, or serrate. The species 

 may be named Tintinntts Fergusonii. Another species of Freia has been 

 detected on the coast of New Jersey, by Professor Leidy, and, from a 

 verbal description given me by Dr. H. C. Evarts, a species occurs in the 

 vicinity of Beaufort, N. C. So abundant was Freia producta in Saint 

 Jerome's Creek that I apprehend that in its free-swimming young state, 

 previous to the time that it commenced to build its test, it afforded not 

 an inconsiderable proportion of food to the oysters jilanted in some 

 parts of those waters. Besides the Freia there were innumerable indi. 

 viduals of VorticeUa observed. One of these had a very thick brown- 



