Ig0 SHARP: HYDRADEPHAGA OF LANCASHIRE AND CHESHIRE. 
so of all the beetles which inhabit the water, the Hydradephaga 
steps by which it has arrived at that high position have been 
more completely erased and become extinct. For, whereas if we 
consider the only other group of the Coleoptera which shows any 
decided modification of structure to subserve a similar aquatic 
environment—that extension of the C/lavicornia which we name 
Palpicornia—if we consider these, I say, we shall at once discover a 
long series of connecting links, a perfect sequence of form from say 
Cercyon, which is entirely terrestrial, on through Spheridium and 
Cyclonotum to Anacena and Laccobius, genera purely aquatic. But 
we detect no such perfect sequence among the Adephaga. ) 
doubt it once existed. Ha/ip/us, though in habit a wholly aquatic 
genus, to some extent acts as a link between Dytiscide and Caradide ; 
and in North America we find that singular genus Amphizoa, which 
is perhaps not so much a present link of union as a relic of some 
archaic form, from whence the ancestors of both groups may 
have been derive 
Hydradephaga, chertone is a very well-defined and quite isolated 
group, and it is impossible to mistake any of its members for species 
of any other division. 
Now, it is a fact worth attention in this connection that most of 
the major divisions of the Coleoptera have their aquatic or semi- 
succeeded best in the prdduccion of the gioup we are considera, 
but Clavicornia are not far behind, as represented by the Palpicornia. 
We know of no British aquatic representatives of the Lamellicornia, 
it is true, but at the other end of Clavicornia we have Purnus, 
Limis, and Heterocerus, all semi-aquatic genera, and in that extension 
of this great division, known as Brachelytra, there are certain of the 
Stent and our one species of Didnous, besides one or two Quedii and 
all the species of Zesteva and Geodromicus, which inhabit the wettest 
moss saturated continually by the spray of waterfalls and mountain 
streams. We have also Diglossa and Micralymma genera almost 
submarine in habitat, and we find many Homalote and Thinobit only 
in the wettest shingle. 
_ Among the hyncophora, the weevils, there are certain dis- 
tinctively semi-aquatic genera, and Euéria and Scirtes exhibit the 
Same tendency in Malacodermi. Even among such a purely plant- 
frequenting section as the Phytophaga, Donacia is a genus whic 
may almost be considered as more aquatic than terrestrial ; 
: ama 
