INFUSORIA. 
69 
and not unfrequently this appears to be composed of minute globules, (ova?) as shown in the 
figure. This species occurs, in vast quantities, in the Hudson river, at West-Point. It may 
be found in some places at low tide, giving to the shores a ferruginous color in spaces even 
as much as a hundred square yards in extent. 
Gaillonella fermginea. Corpuscles very minute, convex on the ends, ferruginous, oval, smooth; having 
the form of articulated threads, often united, almost branching; 30 V 0 t oV 0 
Ehrenberg states with a mark of doubt, that it occurs in all ferruginous waters ; fossil in 
bog iron ore; and in the yellow opal of Bilin. A copy of Ehrenberg’s figure may be seen 
in Lyell’s Elements of Geology, p. 39, (Am. Edit.) and in Pritchard’s Hist. Inf. fig. 129-130. 
I have often seen in bogs and small streams, large quantities of a ferruginous colored fioccu- 
lent matter which dispersed with great ease when touched, and in which I have sometimes 
been able to see, by means of the microscope, excessively minute filaments which were appa¬ 
rently moniliform. I believe these filaments to be the G.ferruginea of Ehrenberg, which is 
the same as the Oscillatoria ochracea of various algologists. The filaments are fragile and 
incombustible, and are said to be composed of silicate of iron. (See Pritchard’s Hist. Inf. 
p. 199 and 200.) 
Actinocyclus. Free; cara/pace simple, bivalve, {siliceous)', form cylindrical, {discoid) divided 
internally by several radiating partitions; spontaneous division imperfect in form of a chain. 
Ehrenberg mentions seven species, viz. A. ternarius, A. quaternarius, A. quinarius, A. 
senarius, A. septenarius, A. octonarius and A. denarius, distinguished respectively by the 
number of cells formed by the radiating partitions. Several species occur in the “ schiste of 
Oran ” in Africa, in a formation which M. Rozet considered as tertiary, but which Ehrenberg 
suspects is more nearly connected with the chalk. 
It appears to me to be an interesting fact, that the remarkable marine infusorial deposit 
discovered by Prof. W. B. Rogers in the tertiary formation of Virginia, appears to agree with 
the infusorial conglomerate of Oran, in containing several species of Actinocyclus, together 
with Gaillonella sulcata, and beautiful punctate discs, which I suspect belong to the genus 
Coscinodiscus. I have seen no account of this last genus, but its name appears peculiarly 
appropriate to the sieve-like discs which form so large a portion of the infusorial stratum of 
Richmond, Va. Ehrenberg mentions Coscinodiscus patina as predominating in the deposits 
of Oran, Zante, Caltasinetta, &c. (See Weaver’s View of Ehrenberg’s Observations in Lond. 
and Ed. Phil. Journ. for May, 1841, p. 393.) In Figs. 9, 10 and 11, are represented several 
fossil species of Actinocyclus from Richmond, Va.; the same species also occur fossil in 
cliffs on the Rappahannock river. In Figs. 12, 13 and 14, are represented the discs which I 
believe to belong to the genus Coscinodiscus. When perfect, the form seems to be that of a 
torus, having the circular bases covered with hexagonal or circular spots, which present con¬ 
siderable variety in their size and arrangement in different specimens. The most usual 
disposition of the spots is in rows corresponding with the radii, as shown in the large speci¬ 
men Fig. 14. In consequence of this arrangement they also form beautiful spiral rows in 
other directions, so that the curves present no inconsiderable resemblance to those often seen 
