36 THOMAS SAY FOUNDATION 
a dark, squarish mark over the ocellar triangle; a pair of lighter 
marks each side of the ocellar triangle; occiput slightly rugulose ; 
antennae of about forty-five segments. 
Pronotum nearly twice as broad as long; brown, with lhghter 
lateral margins; discs somewhat rugose ; angles broadly rounded ; 
front margin nearly straight, hind margin somewhat convex in 
the central area. Legs brown, the tips of the femora and the 
tarsi yellowish. Femora and tibiae fringed with hairs. 
Abdomen eylindric, uniformly brown or with three, more or 
less distinct, longitudinal lighter lines; tenth abdominal segment 
produced into a sharp conical process in both sexes; cerci com- 
posed of some twenty-two segments. Seventeen pairs of tufted 
gills, which are considerably longer than in Pt. regularis and are 
arranged as described under the genus Pteronarcella. 
There seems to be very little difference in the size and structure 
of the nymphs of the two species of Pteronarcella. Pt. badia has 
longer gills than Pt. regularis but otherwise the nymphs appear 
very similar. Pt. regularis probably has a somewhat wider fringe 
of hairs on the tibiae and femora than Pt. badva. 
Reared specimens of Pt. badia from Logan, Utah, and mature 
nymphs of Pt. regularis from Colorado, in which the developing 
genital plate of the female could be clearly seen, have enabled 
me to separate the two species. 
I also have three juvenile forms which apparently are Pt. 
badia because they have been collected in Logan, Utah, where 
the reared specimens of this species were found. These specimens 
measure 5 mm. in length. The nymphs have large spines on the 
legs, thorax and abdomen but seemingly not as numerous as in 
regularis. There are nine pairs of gills located similarly to those 
in the 3.5 mm. size of Pt. regularis. The antennae have about 
twenty-three segments and the cerci about twelve segments. 
Pteronarcella regularis Hagen 
(Plate 12, figs. 179-180.) 
Length of body up to 21 or 22 mm.; antennae up to 9 mm., or 
as long as the entire thorax; cerci up to 9 mm. 
Color brown with some lighter markings, especially noticeable 
on the abdomen of some specimens. 
Head much narrower than prothorax, brown, with lighter 
rounded marks outside the ocellar triangle; occiput somewhat 
lighter, and with faint reticulated markings; antennae of some 
forty-five segments. 
Pronotum almost twice as wide as long; angles broadly 
