FRESH WATER DIATOMS. ‘ 
293 
In the latter case the consistency of the water, in mid-summer, 
was like that of porridge. Unfortunately specimens collected 
from these localities are not now available, and the identity of 
the species concerned in producing this curious effect is not 
known. The occurrence of such vast numbers of living Diatoms 
in situations of this kind goes far to explain the origin of the 
‘‘ Infusorial Earths ” or “ Tripolite ” deposits to be presently 
noticed. 
In the following lists of species it is proposed to give 
( I ) those which are seldom or never found in any other waters 
than those of brooks, rivers above tide water, or ponds and 
lakes, and (2) those of doubtful habitat, found in the lower 
courses of the St. John River and Kennebecasis, where the 
waters are more or less under the influence of tidal flow, and 
where the salinity varies from that of the Bay of Fundy at the 
Falls to where it becomes quite imperceptible. In this latter 
case there is also considerable variation with the depth of water, 
the surface waters being often quite fresh while those a few feet 
down are decidedly salt. And yet again with the seasons, the 
high freshets of spring being sufficient to prevent altogether the 
entrance of the sea-water. As the Diatoms live only near 
the surface where the light can reach them, it is not probable 
that the conditions which prevail in the deeper parts of the 
Kennebecasis, which reaches a depth of nearly 200 feet and the 
temperature in midsummer is about seventeen degrees above 
freezing^ can greatly affect them. 
Lists of Fresh Water Diatoms. 
I. From brook near Biological Station, St. Andrews: 
Diatoma elongatum Ag. 
Diatoma vulgare Bory. 
Cocconema lanceolatum Ehr. 
Gomphonema acuminatum Ehr. 
Epithemia. 
Himantidium arcus W. Sm. 
Melosira. 
Meridion circulare Ag. 
Navicula. 
Tabellaria flocculosa Kutz. 
Pinnularia viridis W. Sm. 
Synedra lunaris Ehr. 
