28 
On the north side of the river the species are often quite differ- 
ent from those on the south side at the same season. Onthis side, 
just within the inlet, is a large flat which is uncovered at low 
tide. Here various species of Amphora may be found; A. 
aponina being usually very abundant during August and Sep- 
tember. On the more sheltered portion of this flat, where the 
flow of water has not been so rapid, the very delicate: Nitzschia 
closterium may often be found in great abundance, also the tiny 
Navicula oculata. On some parts of this flat, however, the col- 
lector may meet with a great disappointment. Spots will be 
found where diatoms are very abundant, but so embedded in 
gelatinous matter as to be almost worthless, for this gelatinous 
material is very difficult to get rid of in cleaning. Besides, it 
retains a great deal of sand with the diatoms. The best plan is to 
avoid collecting such stuff, but collect as near the water’s edge 
as possible, Here the diatoms have been washed clean by the 
constant action of the water and deposited in little winrows 
along the sand-ripples, the flocculent matter having been washed 
away. Upon the large flat just east of the wagon bridge, 
Navicula lyra and N. forcipata may often be found abundantly, 
but the collections made here are not apt to be so pure. Be- 
_ Sides the species enumerated as occurring nearly pure, there are 
many other species which may be found more or less abundantly 
in mixed gatherings. These may be gleaned from the list at the 
close of this paper. 
Above the railroad bridge, the river broadens out into a bay 
over a mile in width, and this is a veritable treasure house to the 
diatomist. In some parts of this bay, at certain seasons, the 
growth of alge is so dense that it is difficult to row a boat 
through it. In June there is comparatively little to be found 
here, but, as the season advances, the growth of alge and of 
diatoms is more prolific. By the second or third week in 
August, Achnanthes brevipes is exceedingly abundant upon 
Polysiphonia Harveyi, about two hundred yards west of Buhler’s 
wharf. Farther west, Striatella unipunctata, Synedra fulgens, 
the ordinary species of Grammatophora, Epithemia musculus 
and Melosira nummuloides are often very abundant. Here 
every piece of seaweed should be separately inspected and so 
