; 
rw 
Sketch of the Tafusoria of the family Bacillaria. 91 
3. Gaillonelia distans. (Pl. 2, fig. 5.) Corpuscles cylindrical, 
short, truncate and flattened on the ends, smooth, with two pierced fur- 
rows, always separated in the middle, >4+¢ to 74 line, usually Jy. 
This species occurs in vast quantities in the fossil state in Ku- 
rope. It constitutes a large portion of the slate of Bilin and Cas- 
sel, and of the “ Berghmehl” or “fossil farina” of various locali- 
ties. It occurs in most of the specimens of American fossil in- 
fusoria, which I have seen. It is particularly abundant in the 
specimens from Manchester, Mass., which are chiefly composed 
of exceedingly minute frustules of this species. It forms here, 
a true fossil farina, almost as light as flour, and containing ina 
cubic inch many hundred millions of these minute siliceous shells. 
It oceurs in a living state at West Point. 
4. Gaillonella varians. (Pl. 2, fig. 6, a, b.) Corpuscles flat on 
each end, cylindrical surface smooth, ends with fine radiating lines, 
ovaries yellow or green, +3 to gly line 
Our fig. 6, represents a species which is not uncommon in 
ponds near West Point. The discoid surfaces of the individuals 
show minute radiating lines quite distinctly. 
5. Gaillonella sulcata. (Pl. 2, fig. 7, a,b?) I noticed frag- 
ments of this species two years ago in peat from a salt marsh 
near Stonington, and among marine Alge in the same vicinity. 
I had prepared a sketch and description of it for this memoir, 
before I heard of the discovery of the infusorial stratum of Vir- 
ginia. _I was, therefore, agreeably surprised to find, on inspect- 
ing ‘specime ens of the fossil infusoria from Richmond, Rappahan- 
hock Cliff, &c., that this species was very abundant in them. A 
careful comparison of the recent specimens from Stonington, 
and the fossil specimens from the tertiary of Virginia, has left no 
doubt in my mind of their specific identity. The following is 
the account of the recent specimens, written several months be- 
fore the reception of the Virginia fossils. ‘They consist of frus- 
tules, each of which is divided by a transverse line ; the cylindr?- 
eal surface of each frustule has a great number df parallel ities 
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 in- 
fusorial 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 7 Survey of 
