242 
GEOLOGY OF THE FIRST DISTRICT. 
Section IV. LACERNATA. 
Frustulia, Envelope double; carapace siliceous; mantle gelatinous; amorphous; corpuscles 
scattered or in groups. 
I have seen no American species of this genus.* 
Syncyclia. Envelope double; exterior mantle gelatinous; carapace siliceous, navicula-shaped; 
forming by spontaneous'division, circular groups surrounded by gelatine. (See Pritchard’s 
Infusoria, Plate 4, p. 206.) 
No American species has yet been detected. 
Naunema. Envelope double; carapace navicula-shaped, siliceous; mantle gelatinous, exterior tu¬ 
bular ; tubes filiform, separate, branching, confervoid, resulting from perfect division of the 
carapace, and imperfect division of the mantle. 
In this genus, corpuscles which cannot be distinguished from those of Navicula are assem¬ 
bled together in vast numbers, in flexible membranous tubes, within which they may often 
be seen to move freely. They doubtless often leave these tubes, and then appear like species 
of Navicula. 
I have noticed several American species, but I am unable to decide whether they are iden¬ 
tical with any hitherto described, as I have had very little opportunity to study our species in 
a living state, and have no foreign specimens or figures to compare them with. I shall there¬ 
fore content myself with merely giving the forms of the frustules found in each species, and 
such additional particulars as seem most interesting. 
Naunema -. (Pi. 42, fig. 14.) The figure represents corpuscles from a branching species found 
on the shores of Staten island, N. Y. The tubes are whitish, containing long^rovvs ol' corpuscles, 
strung end to end, each of which contains two round globules looking like air-bubbles. No trace 
of striae. 
Naunema -. (Pi. 42, fig. 15.) This figure shows the form of corpuscles which filled short 
robust unbranched filaments, which were exceedingly lubricous. Bunches of filaments about half 
an inch in length, were found in great abundance on Zostera, &c. at Stonington, Conn. 
Naunema -. (PI. 42, fig. 16.) This figure shows the outline of dried corpuscles from a speci¬ 
men obtained at Stonington, Conn., where it is very common. Its filaments are branched, and 
form larger and longer bunches than the preceding, with which it occurs. 
Naunema -. (PI 42, fig. 17.) This is from specimens found in immense quantities in the Hud¬ 
son river, at West-Point. The masses have not the green color of the two preceding species, but 
present a rich brown color. The frustules are in all respects like those of Navicula, and I have 
often seen them move spontaneously in their tubes, some going one way and others another. 
In PI. 42, fig. 17, a, is shown the outline of much longer frustules, found in tubes similar 
to those just mentioned. 
♦ My opportunity to study the marine Bacillaria has been very slight. I presume, therefore, that many marine forms not no¬ 
ticed by me during the two days which 1 spent at Stonington will yet be detected, and among them will probably be species of 
Frustulia, Syncyclia and Schizonema. 
