202 SHARP: HYDRADEPHAGA OF LANCASHIRE AND CHESHIRE. 
A. unguicularis, taken by Mr. Chappell, Withington, Rusholme, 
Cheshire. 
Platambus (flattened) is another genus, with one species, 
P. maculatus. 1 have taken it abundantly in the Alyn, at Gresford, and 
doubtless it would occur among the shingle on the right bank of the 
Dee, which would bring it into our district 
Copelatus (the rower), formerly Ziopterus (smooth-winged), has 
also one species, C. agi/is, which I have so far never met with, but it 
occurs generally over the district. 
Rhantus and Colymébetes were formerly combined under one 
genus Colymbetes. According to Canon Fowler’s arrangement, 
however, Colymbetes (the diver) has but one species, C. fuscus, a large 
insect like a Dytiscus, which is common generally, and particularly 
abundant in the shallow lagoons formed on the sand-hills. 
The other division, now Rhantus (which I think means sprinkled, 
in allusion to their dotted elytra), represents six species. Three have 
been taken here. Dr. Ellis took a dead specimen of 2. exoletus once 
on the banks of the Alt; 2. grapiz, one specimen taken by Mr. Gregson, 
in Mosslake Fields, and also by Mr. Chappell, near Pendleton ; and 
R. bistriatus, taken by myself in Delamere cies 
fe now come to the Dy/iscina group of gener. 
Dytiscus itself (made like a diver); Basie liciliide tensive 
pointed), and Graphoderes (scratched or striated skin). 
Dyitiscus contains the largest and best known of all the water 
beetles. D. marginatus is the commonest, but D. punctulatus has been 
taken at Wallasey and in Delamere. Of six species of this genus, 
we only possess these two. Neither of the two Aydatici are recorded. 
Of Actlius, A. sulcatus is fairly common, the other one, A. canaliculatus, 
is recorded in Mr. Cosmo Melvill’s list of the Manchester Coleoptera, 
but the record may be a mistake for A. su/catus, as these two species are 
very sifnilar. 
The remaining genus of the Dytiscide, Graphoderes, contains one 
species, which is supposed to be extinct as British 
We have now merely to allude to those two genera which form 
the family Gyrinidz, which as we have seen differs so materially 
from any other of the families of the Adephaga. Gyrinus (the 
whirler) numbers nine species, which it seems to me are among the 
most difficult of all the Coleoptera to satisfactorily determine. We 
have records of four species, two of which are very common, G. marinus 
and G.atator. ‘The commonest species about my own district seems 
.to be G. marinus, and Mr. Chappell says the same of the Manchester 
locality. Mr. Gregson took the rare species, G. dicolor, from Raley, 
in Cheshire, and Mr. Chappell and others have met with G. distinctus 
Naturalist, 
