66 THOMAS SAY FOUNDATION 
short spines. Labium half again as long as wide; glossae short; 
paraglossae very long, somewhat incurved at the tip and beset 
with many long hairs; hypopharynx broadly rounded, very close- 
ly beset with short hairs, and extending almost to the tips of the 
paraglossae; mentum broadly triangular; submentum very little 
wider than long, its anterior angles broadly rounded and pro- 
longed; first segment of palpus a little longer than wide, second 
segment twice as long as first, and third segment almost two- 
thirds as long as second but less than half as wide; tip of third 
segment with a few hairs. 
This species bears no gills. 
Described from one nymph and many nymphal skins collected 
at Bozeman, Montana, by R. A. Cooley; and one nymphal skin 
from Logan River, Utah, by J. G. Needham. 
Nothing is known about the biology of this species, but, judg- 
ing from the structure of the mouth parts, it is undoubtedly a 
carnivore and probably lives in swift water. 
Genus NEOPERLA Needham 
This genus is readily recognized by the fact that the nymphs 
possess only two ocelli, which are set close together. The color in 
live or freshly killed specimens is a combination of yellow and 
brown. The gills are very long and the legs bear fringes of long 
delicate hairs. 
Head as wide as prothorax, or slightly wider; labrum brown 
on anterior margin, followed by a narrow transverse yellow band 
which in turn is followed by a wide brown transverse band; rest 
of head yellow except sometimes with brown around and behind 
ocelli; occipital ridge very distinct; ocelli usually set very close 
together, the distance between them hardly more than the diam- 
eter of one occellus, although in immature nymphs they are spaced 
a little farther apart; antennae yellow and at least half as long 
as the entire body. 
Labrum about four times as wide as long. Mandibles somewhat 
asymmetrical. Right mandible with five sharp, unequal teeth, 
the outer tooth the largest ; following the teeth, the inner margin 
is fringed with long hairs. Left mandible with six unequal teeth 
more or less arranged in groups of three each. 
Maxillae: first segment of maxillary palpus short, and about 
as long as wide, second about twice as long as first, third and 
fourth subequal, each about as long as first and second together, 
fifth segment about half as long as fourth and only about half 
as large in diameter. Lacinia broad at base, produced into a long, 
