Sketch of the Infusoria of the family Bacillaria. 325 
boat-shaped frustules of Cocconema will generally serve to iden- 
tify them. 
1. Cocconema (Pl. 3, fig. 10.) Carapace lanceolate, ends 
obtuse, pedicels repeatedly dichotomous, secondary branches articula- 
ted to the primary ones. Strie were not perceived. 
Abundant in the Hudson River at West Point. It appears to 
be allied to C. lanceolatum of Agardh. 
2. Cocconema (PL. 3, fig. 11, a, b.) These figures repre- 
sent two positions of a species of Cocconema which is very common in 
the living state near West Point, and which also abounds as a fossil. 
In the living state I have but rarely seen it attached to a pedicel. It is 
generally free, and moves about spontaneously like a Navicula. 
once, on a cold day in October, noticed vast collections of this 
species which were enveloped in a mucous covering, and which 
formed large cloud-like masses several inches in extent, investing 
aquatic plants, stones, &c. Each of these masses was crowded 
with millions of the siliceous shells of this species. 
Ehrenberg mentions C. asperum as a new species detected by 
him among the fossils from West Point. Iam ignorant of its 
distinguishing features. 
‘ 
ACHNANTHES. 
Carapace simple, bivalve, or muliivalve, elicits, prismatic, 
longer than broad, fixed by one end, pedicellate, pedicel oblique, 
ventral, always simple, opening in the middle of the body. Groups, 
resulting from increase by spontaneous | longitudinal division, re- 
sembling chains, little banners, plates or ribbons. 
Achnanthes brevipes. (Pl. 3, fig. 12.) Corpuscles striate, curved 
in the middle, ends rounded on the dorsal and ventral sides; pedicel 
thick, shorter than the body. 
I first noticed this species on fileariecite of Coniferve Sites from 
Providence Cove, R. I., and have since found it abundant on ma- 
rine Alge from Stonington, Conn. Small specimens, differing I 
believe in no essential character, are also very abundant on aquatic 
plants in the Hudson River at West Point. 
~The Achnanthes longipes of authors may be a distinct species, 
but the distinction “ pedicel longer than the body,” appears to me 
to be founded on a character liable to much variation. I saw spe- 
cimens at Stonington having pedicels much longer than the body, 
yet they appeared to me oe with cab eta se 
