168 
Calothrix scopulorum, Ag. 
Common. 
Calothrix crustacea, Thuret. 
Nahant (Frank S. Collins). 
Rivularia atra, Roth. 
New England (Dr. Farlow’s list). 
Clathrocystis roseo-persicina, Cohn. 
New England (Dr. Farlow’s list), Gloucester (Mrs. Bray). 
ADDITIONAL SPECIES. 
Mesogloia vermicularis, 4g. 
“Occasionally found at Cape Ann” (Dr. Farlow, in Proc. Am. 
Acad., Vol. X), Gloucester (Mrs. A. L. Davis, in herb. P. A. S.). 
Rhizoclonium Kochianun, Kiitz. 
‘¢ Lynn beach, and since found at Gloucester” (Frank S. Collins, in 
letter of Nov. 24, 1879). 
Rhizoclonium riparium, Harv. 
This will be found in Essex county, as it belongs to this region. 
Monostroma pulchrum, Farlow, n. sp. 
Nahant (Frank 8. Collins). 
Notr.—The fresh-water Alge of the county have not received 
sufficient attention from any one to make it possible to present here 
a list even of the larger and more conspicuous species. Like the 
Fungi, they contain immense numbers of microscopic species, many 
of which have not been studied enough to be arranged in their proper 
places. Among the lower forms are the Diatoms, which are also 
found in salt water, and perhaps it is well to mention that the Proto- 
coccus nivalis (or Red Snow of the Arctic Voyagers) has been 
observed at Nahant. 
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