Sketch of the Infusoria of the family Bacillaria. 93 
ing to the shores a ferruginous color in apeers even as much as a 
hundred square yards in extent. 
7. Gaillonella ferruginea. Guptinies very einai convex on the 
ends, ferruginous, oyal, smooth, having the form of articulated. threads, 
often united, almost branching, sol to zoho line 
_ Ehrenberg states with a mark of doubt, that it occurs in all 
Seeainived waters ; fossil in bog iron ore; and in the yellow 
opal of Bilin. A copy of Ehrenberg’s- hoops may be seen in 
Lyell’s Elements of Geology, p. 39, (Am. Edit.) and in Pritch- 
ard’s Hist. Inf. fig. 129-130. I have often seen in bogs and 
small streams, large quantities of a ferruginous colored floculent 
matter which dispersed with great ease when touched, and in 
which I have sometimes been able to see, by means of the micro- 
cs aatigarniceti minute filaments which were apparently mo- 
nili I believe these filaments to be the G. ferruginea of 
ing which is the same as the Oscillatoria ochracea of va- 
rious 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. 
tee carapace simple, bivalve, (siliceous) form cy lindrical, 
| ( discoid ) divided internally by several radiating partitions ; spon- 
tancoite Hiviaien: imperfect in form of 4 chain. 
_ Ehrenberg mentions seven species, viz. A. ternarius, A. qua- 
‘iiainn 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 
ot 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 in- 
fusorial conglomerate of Oran, in containing several species of 
Actinocyclus, together with Gazllonella sulcata, and beautiful 
punctate discs, which I suspect belong to the genus Coscinodis- 
cus. [have seen no account of this last genus, but its name 
appears peculiarly appropriate to the sieve-like discs which form 
$0 large a portion of the infusorial stratum of peer Va. 
“Ehrenberg mentions Coscinodiscus patina as pred 
