44 
The labium extends posteriorly beyond the bases of the 
second pair of legs. The median lobe is considerably produced, 
and rather deeply cleft in the middle, the angles each side of 
the cleft minutely rounded. Lateral lobe squarely truncate on 
the end, with a minute tooth terminating the inner border, 
which is finely denticulate. Movable hook long and arcuate. 
Supracoxal processes of equal length, a little obtuse, pointing 
in slightly diverging directions, the angle between them about 
75 degrees, the posterior a little broader. 
Abdomen with lateral spines on segments 5 to 9, increasing 
in length posteriorly, those of 5 very minute and rudimentary, 
of 6 somewhat appressed, of 8 and 9 nearly equal, of 9 three 
fourths as long as the 10th segment at middle. Appendages 
longer than segments 9 and 10, inferiors longest, slightly in- 
curved at tip; superior four fifths as long as inferiors, exactly 
intermediate in length between the two pairs, a pair of short 
spines at its terminal angles, between which the tip is semicir- 
cularly notched, sides parallel and fringed with fine hairs, its 
basal male enlargement elongate, triangular, scale-like, cover- 
‘ing its basal three sevenths ; laterals three fourths as long as 
superior, cylindrical, abruptly acuminate apically. 
3. Alschna sp. (a). 
A number of small nymphs from Yellowstone Park and 
.Montana, 15 mm. and less in length, appear to be different 
from any others known to us. The lateral spine on the sixth 
segment is very small; on the fifth segment there is merely a 
smooth angulation ; the rear angles of the head are very slightly 
or not at all rounded. The supracoxal processes are exactly 
equal and similar. The very young individuals (7.5 mm.) are 
not transversely banded. The nymphs are too young for any 
comparison of the lengths of the terminal appendages. They 
were collected July 25 to August 19 from bark and rotten logs 
ina bayou of Flathead River, near Demersville, Montana, and 
in Yellowstone Park from the Gibbon River and a lagoon of 
geyser water near Lewis Lake. 
