[Nove, 
Genus Centboptilum,* u. g. 
Sp. typ. O. luteolum, Mul. 
Sjn. Ephemera, p., Miil., 1776, 
Cloeon, p., Ste., 1835-6 ; Cloe, p., Burm., 1839. 
Baetis (Leach), section A. Etn., 1868. 
-Dmgrnosis.— Nymph agile, with seven simple pairs of undivided branc 
plates. Upper maxillary palpus slender, rather long, 4-jointed, with the firstj: 
the shortest, the second long and equal in length to the other two taken togeti 
which are sub-equal to each other. 
The sub-imago assumes the same posture as Baetis when reposing. 
Imago similar to Cloeon ; but with four wings. Hind-wing very naiTow, v 
a long costal process, and two simple longitudinal veins. 
Distribution.— The Palsearctic and Nearctic regions. Two Ei 
pean species are described, one of which (G. luteolum) occurs also in 
Hudson's Bay Territory. Besides these, there are an English an( 
Carinthian species known to me, undescribed. 
Unfortunately I cannot just now lay my hands upon either sp 
mens of the nymph or preparations of the mouth organs of O. luteolu 
therefore I am unable to speak positively about the structure of 
labium and lower maxillao ; but, so far as I can recollect, these arem 
like those of Baetis than of Cloeon. The labrum is widely retuse, u 
EpTiemerella. 
In Oloeon the palpi are two-jointed, with sub-equal joints : 
upper maxillary palpi are very slender, filiform, and rather longer tl 
their maxilla : the lower maxiUary palpi are slightly depressed, i 
somewhat expanded towards their oblique tips ; and their maxilla ; 
a little longer, but no broader than the divisions of the labium. 1 
labrum is narrowly emarginate. 
In Baetis the palpi are likewise two-jointed, with joints sub-eqi 
to one another : the upper maxillary palpi are slender, of tolerably ev 
diameter throughout, and not so very long : the lower maxillary pa; 
are depressed and broadly expanded towards their rounded tips, t 
basal joints being sub-cylindrical and stout; their maxiUfe are lo'n^ 
and much broader than the somewhat subulate divisions of the labiu 
The labrum is narrowly emarginate. Professor Pictet's figure of t 
labium and lower maxiUs with their palpi (Pict. EpJiem., pi. xxxvi, 
is not accurate. 
The mandibles are much alike in all of these three. 
Ashbourne, Derbyshire. 
\htli September, 1869. 
proce«s'i7tri'hi;;7Jwinl'''"''''''' "" ''"'' *"' ^''"""'' "^ -*"'^' 5 «o named in allusion to the cos 
