BIOLOGY. it 
Silver Lake, or in the forty-four slides of Cincinnati diatoms, was quite abundant. 
Only one Navicula of the rhomboides type was seen, and that was a variety, 
the Colletonema vulgare of Thwaites. Stawroneis phenicenteron, one of the 
few distinctively fresh-water forms said to be found everywhere, was not met 
with. 
Epithemia gibba, so remarkably abundant at Topeka, was present, but 
rather uncommon. Of the three or four species of Nitzschi@, only one seemed 
to be of common variety, and one of them, Nitzschia sigma, is catalogued by 
different authorities as a marine form. A most remarkable thing was that not a 
single Surirelia of any kind was seen in the three slides mounted. As they are 
one of the most abundant forms everywhere, and there being plenty near at 
Medora, we must either conclude that there were none where the fish lived, or 
that they possessed some poisonous or other undesirable qualities which caused 
him to reject them. 
One of the most remarkable things found was the Mastagloia (fig. 20, pl. III). 
The genus is almost exclusively marine or brackish, and only one of the two spe- 
cies are ever found in fresh water, and they are excessively rare. This one, M. 
lacustris, was not found at Cincinnati; though an allied species, MW. lanceolata, 
was recognized there with some slight reserve. It is also catalogued by Thomas 
and Chase, but none of either was found at Gage’s pond or Silver Lake. 
Fig. 7, pl. II, seems to be what Grtinow calls Nilzschia apiculata, though 
the blank line down the center and the absence of alea seem to identify with 
Synedra. 
To give an idea of the relative proportions of the genera present in a field of 
view one-fiftieth of an inch in diameter, selected merely because it had an Am- 
phiprora in it, so as to include that, there were the one Amphiprora, one Am- 
phora, one Cymbella, two Nitzschie, three Pleurosigme, and thirty-four 
Navicule. 
The genera and species, so far as observed, were as follows: 
Awmphiprora conspicua(?), (perhaps col- 
umetica?). 
Amphiprora paludosa W.S., said to be 
British (fig. 9, pl. IT). 
Amphora cymbifera Greg. 
Amphora lineata (fig. 15, pl. IIT). 
Awmphora (No. 18, Schmidt’s Atlas, pl. 
39). 
Cocconeis pediculus. 
Cocconema australicum A. S. 
Cocconema cistula. 
Cocconema helveticum. 
Cocconema hungaricum. 
Cocconema lanceolatum. 
Cocconema mexicanum. 
Cyclotella rotula. 
Cyclotella (a small unknown). 
Cy mbella affinis. 
Cymbella gastroides. 
Cymbella helvetica. 
‘Cymbella kamchatica Grtin. 
‘Cymbella minuscula Griin. 
‘Cymbella (No. 40 of Sch. 9, not named). 
Cymbella stomatophora. 
Cymbella tumidula. 
Cymbella turgidula. 
Cymbella (two small unknown). 
Denticula splendens. 
Encyonema lunula. 
Epithemia gibba. 
Epithemia gibba, var. ventricosum. 
Epithemia gibberula. 
Epithemia (like musculus, but ends not 
so sharp). 
Epithemia (uncertain, fig. 21, pl. III). 
Epithemia zebra. 
Gomphonema abbreviatum. 
Gomphonema angustatum, var. inter- 
media. 
Gomphonema capitatum. 
Gomphonema clavatum. 
Gomphonema commutatum. 
Gomphonema commutatum, var. sub- 
ramosum., 
Gomphonema intricatum, var. pumila. 
Gomphonema olivaceum. - 
