~ 
on the Ephemeride. 53 
and their relative sizes. In some genera there is a 
minute pair of branchial processes on the first abdominal 
segment, which is very liable to be overlooked. Some- 
times the anterior pairs of plates differ in texture and 
form from those of the segments behind them. These 
last items have more to do with the determination of the 
order of succession of genera closely allied to one 
another, than with the determination of the position of 
a genus in the family at large. 
Arrangements of genera founded upon the structure 
of the imago, or of the nymph, alone, can be only tem- 
porary. ‘The relations of genera can be definitely ascer- 
tained, only by taking into consideration all the peculiari- 
ties presented by the structure of representative species 
at the principal epochs in the course of their develop- 
ment from the egg. 
NOTANDA. 
long. al.=longitudo coste ale antice. 
exp. al.=explicatio alarum anticarum. 
set.=longitudo setarum caudalium; e.g., sub Ephemera vulgata legitur 
“ set. 33 & 34-32 & 36 mm.” i. ¢., longitudo setarum exterioris 33-32 
mm., interioris 34-86 mm. 
mm.=millimetres; mensurd Gallicé adhibita. 
im. & subim.=imago et subimago. 
Symbola descriptionibus preeposita significant,— 
Vv. S.=viyum specimen. 
vy. vy. Ss. = vidi specimen vivum. 
8. S.=specimen siccum. 
VY. 8S. 8. vidi specimen siccum. 
} !=vidi specimen genuinum siccum. 
* Cum terminologid doctoris Julii Miiller,* terminologia colorum una et 
eadem est, preter in locis sequentibus :— 
Testaceus et luridus concolores putantur. 
Isabellinus, Miil,=furfurosus (Anglice, bran-colour). 
Fuscus et umbrinus, Miil., similiterque olivaceus et pistazinus, Miil., con- 
colores esse putantur. 
Ferrugineus= Anglice, steel-blue. 
Rubiginosus= Anglice, rust-red. 
* Terminologia Entomologica. J. Miller. Briinn, 1860. 
