68 
GEOLOGY OF THE FIRST DISTRICT. 
Gaillonella sulcata. (PL 22, fig. 7, a, b ?) I noticed fragments of this species two years 
ago in peat from a salt marsh near Stonington, and among marine algae in the same vicinity. 
I had prepared a sketch and description of it for this article, before I heard of the discovery of 
the infusorial stratum of Virginia. I was, therefore, agreeably surprised to find, on inspecting 
specimens of the fossil infusoria from Richmond, Rappahannock cliff, &c., that this species 
was very abundant in them. A careful comparison of the recent specimens from Stoning¬ 
ton, and the fossil specimens from the tertiary of Virginia, has left no doubt on my mind of 
their specific identity. The following is the account of the recent specimens, written several 
months before the reception of the Virginia fossils : They consist of frustules, each of which 
is divided by a transverse line ; the cylindrical surface of each frustule has a great number 
of parallel lines in the direction of the axis, and the ends or flat surfaces show a rim having 
lines corresponding to those on the cylindrical surface; within this rim is a diaphragm having 
minute radiating lines. Chains of thirty or forty individuals are not unfrequent in the infu¬ 
sorial earth of Richmond, particularly in the upper part of the stratum. These are doubtless 
the “ oblong cylinders ” alluded to by Prof. W. B. Rogers in his Report on the Geological 
Survey of Virginia, p. 39. Ehrenberg gives the following description of Gaillonella sulcata, 
a fossil species occurring in the schist of Oran; from this description I suspect it to be closely 
allied to our species, and therefore copy its specific characters for the purpose of comparison. 
“ Gaillonella sulcata. Corpuscles cylindrical, short, truncate at the two ends and flattened, furrowed 
across and in form of cells (sillonnes en travers et sous forme de cellules); -Jg to line.” * 
Gaillonella? -. (PI. 22, fig. 8.) Corpuscles long, cylindrical; with two lines of constriction, ad¬ 
hering by alternate angles so as to form long zigzag chains, and occasionally auricled. 
The curious bodies represented in PI. 22, fig. 8, appear to partake of the characters of 
both Gaillonella and Bacillaria, showing the cylindrical corpuscles of the former, united by 
alternate angles as in many species of the latter. It is, perhaps, related to Diatoma auritum 
of Lyngbye, which is described as having the “joints quadrangular, rounded, with an auricle 
at each angleand of which Greville remarks, that the auricular appendages of the angles 
give to the frustules the appearance of “ microscopic woolpacks.” Having seen no figure or 
specimen of D. auritum, I cannot decide as to its identity with our species ; I believe, how¬ 
ever, that ours must be different, both from its abundance, and from the remark of Kiitzing 
Linnaea, 1833, p. 585) that D. auritum probably belongs to the Desmidiaceas. 
Our species consists of large cylindrical siliceous joints, usually adhering together by 
alternate angles in a zigzag manner. Most of the frustules show two lines of constriction, 
as shown in the figure. The connection of the frustules is by a very conspicuous, flexible 
hinge-like ligament, which often gives to the joints an auricled appearance, which makes the 
comparison of them to “ microscopic woolpacks,” or rather bales of cotton, not inappropriate. 
The joints usually contain a yellow or ochraceous substance, arranged in a stellate manner. 
* In Pritchard’s History of Infusoria, recent and fossil, I find a figure of Gaillonella sulcata, which leaves no doubt that our 
fossil specimens from Richmond, as well as our recent ones from Stonington, belong to this species- The living animals have 
also been detected at Cuxhaven, by Ehrenberg. See appendix to Pritchard’s work, p. 434. 
