564 Mr. Kenneth J. Morton on 
brownish-grey, with darker pterostigma and fuscous or blackish 
neuration. The lateral appendages of the ¢, viewed from the 
side, are rather broad and rounded at the base, the shaft slender 
and subcylindrical, bent beyond the middle and continued out- 
wards into a subacute point ; viewed from beneath, the apical part 
of the appendage is turned outwards in the form of a thick hook ; 
inwardly, the chitinized part is prolonged into a spur, under which 
is a membranous space. Exp., 12 to 18 mm., the ? the larger. 
The smaller size and less hyaline wings will ordinarily 
suffice to distinguish this species from the last; the form 
of the appendages is constant in all the material I have 
examined, and I have never noticed any tendency in 
them to assume the upturned position they occupy in the 
last; in the present species they are also much more 
slender. 
This is one of the commonest Nemoure of all the 
streams of North Britain wherever I have collected. It 
kas occurred by all sizes of running waters, from the 
larger rivers to the tiniest rills, the size of the insect 
varying according to the extent of the waters it inhabits. 
It has not yet come before me from the Continent. 
The application of the name cambrica is open to 
question. The only type seen by me is a ?, and, there- 
fore doubtful. N. pallicornis and N. nitida are both 
represented by females without abdomen ; they are more 
probably large examples of the species which I have 
named N. inconspicua. 
Nemoura lateralis. 
N. lateralis, Pictet, Mém. de la Soc. de Phys. et 
d’Hist. Nat., vu., p. 180 (1836); and Perlides, 
p. 895 (1841); ¢ (2). 
N. nitida, Pictet, Mém. Soc. Phys., p. 179; and 
Perlides, p. 392; 9 (7). 
Head and thoracic segments brownish, or black mixed with 
brown, margins of pronotum paler. Antennz concolorous with 
head, basal joint often paler. Pronotum about same breadth as 
head without the eyes, with margins moderately distinct, receding 
very little posteriorly. Legs yellowish, femora above marked with 
fuscous, as are also the tips of the tibie, and the tarsi. Wings in 
the ¢ usually nearly hyaline, in the ¢? rather more greyish, 
neuration fuscous, membrane faintly clouded about the x nervures 
and pterostigma, The appendages of the ¢, from whatever aspect 
