LUCY WRIGHT SMITH 
457 
Abdomen cylindric, the tenth segment narrow below, prolonged 
above into a triangular process ending in a sharp spine (fig. 34); 
the supra-anal plate, a rounded fleshy lobe, attached to the 
ventral surface of the tenth dorsal segment (fig. 34 Sup. A. P.) ; 
the sub-anal plates, triangular, divergent at the tips (fig. 34 Sub. 
A. P.). Setae, slender, tapering, a little more than a third as 
long as the body. 
Seventeen pairs of tufted tracheal gills on the ventral side of 
the thorax and the basal segments of the abdomen, arranged in 
the following manner, three pairs in the integument of the neck, 
forming a collar, one pair (much smaller) on the lateral anterior 
margin of the base of the front legs, four pairs arranged around 
the posterior margin of the same pair of legs, a single pair on the 
median anterior margin of the base of the second pair of legs, 
three pairs arranged around the posterior margin of the base of 
the third pair of legs, one pair (much smaller) on the lateral 
posterior margin of the same legs; three pairs, one on each of the 
first three abdominal segments (fig. 33). 
Morphological Notes 
The genus Pteronarcella is as yet so little known that the litera- 
ture contains absolutely no biological and morphological data 
concerning it. 
Figure E . — Pteronarcella regidans Hagen. Supra-anal plate 
in left lateral view. 
Although the supra-anal plate of the male is normally com- 
pletely hidden, it has been dissected out in Pteronarcella regularis. 
It is of considerable interest in establishing a further bond of 
kinship between this genus and Pteronarcys. It is through the 
proteus type of Pteronarcys that the relationship can be traced. 
The supra-anal plate consists of the same essential parts although 
decided differences in detail are very evident. 
TRANS. AM. ENT. SOC., XLIII. 
