1868.] 
178 
images, which differ from the % imago of nehulosus Walker, Q^ndo^ia- 
fus Walsh,) described above as coming from Saskatchawan, in the 
head and prothorax being marked with yellowish, the anterior legs 
brown, the exterior setae white with larger black incisures on their 
basal half, and the wings hyaline. The ovarian valve is pale, oval, 
deeply excised and bifid on the apical half. Length 9 9 mill. Ex¬ 
panse 9 25—28 mill. Ext. seta 9 15 mill; intermed. seta 9 8 mill. 
Ant. leg 9 7 mill. It is difficult to determine whether this 9 belongs 
to P. odonatus or to P. cupid.us^ for, as before stated, I received S S 
of both these species from the same locality. [See note 15.] 
It will thus be seen that I reduce the four described N. A. species 
of Potamanthus to two. After all, it is possible that they may be dif¬ 
ferent ) but with the materials before me and the published descrip¬ 
tions, it is impossible to be sure of the fact. 
It is remarkable that the American species of Potamanthus consti¬ 
tute a special group, from the fact of the intermediate seta being much 
slenderer and shorter than the exterior seta, while in the Potamanthus 
of Europe they are equally robust and equally long. 
Palingenia. 
In Ephenierina there is no doubt that many new genera will have 
to be established. Csenis, Oligoneuria^ and Ephemera^ are good genera, 
and the few known species resemble one another. But Potamanthus^ 
Palingenia^ Bsetis and Cloe will have to be separated, and M. Pictet 
himself has perceived that these genera are composed of very different 
types. Palingenia^ for example, ought to be separated as follows :— 
1. Palingenia. Wings large, opaque, with numerous cross-veins. 
Two very long setse % or short and hairy 9 ; the intermediate seta very 
rudimentary. Anterior legs % more robust, of moderate length, with 
the femora equal in length to the tibiae; the other legs feeble, short 
and in a rudimentary state; the first joint of the tarsi free in the ante¬ 
rior legs alone. The 9 remains in the subimago state and does not 
moult. Eyes % almost contiguous. Ancient type— P. longicauda 
Swammerd. P. fuliginosa Boch. (Black Sea.) P. lata Walker (Sil- 
het.) P Weber (Brazil.) P. dorsalis Buxm.l (Brazil; I 
am only acquainted with 9 .) 
2. Biffert. Eyes widely separated. Intermediate seta 9 long 
as the others, hairy at the tip. Anterior legs % slender, very long, 
