On Aquatic Carnivorous Coleoptera or Dytiscide. 893 
at present to attempt a natural classification of them, based on the whole of their 
structures. The peculiar sculpture of the wing-cases offers however a very simple 
means of arranging the species in groups, and I have accordingly made use of it, 
and classed the species in fourteen groups. Seven of these groups have, in addition 
to the conspicuous strize, a submarginal stria placed very near the outside of the 
wing-case, quite close to the irregular punctures near the epipleural margin ; this 
stria is of variable length, sometimes quite short; in groups 1 to 7 no trace of it 
exists. 
I. 55.—Genus AGL YMBUS. (Vide p. 596.) 
This aggregate is formed by seven species ; they are similar in most respects to 
Copelatus, and possess on the upper surface a beautiful and conspicuous sculpture 
of very short lines. The hind coxe are very large ; the wing of the metasternum 
terminates as a slender band abruptly deflexed outside the front part of the coxa; 
the coxal lines are quite obliterated, the coxal lobes are shaped as in Copelatus 
and possess a well marked incision. 
The aggregate is allied to Copelatus, differing from it in the obliteration of the 
coxal- lines ; all the species, except A. brevicornis, have the spaces which should be 
included between them (if they were not obliterated) broader than in Copelatus ; 
A. brevicornis departs however from the other species in this respect and is similar 
to Copelatus by the excessive reduction of these spaces. It 1s highly probable 
that this species, and probably also A. gestroi, should be separated from the 
others; and even then it is possible that the remaining South American species 
could not properly be included in one genus. The species are however so exces- 
sively rare, that of most of them I have seen only a single individual, and in 
several cases I have no specimen now before me for comparison and verification 
and have merely to trust to the imperfect notes made when I drew up the deserip- 
tions of the species. 
The following additional characters are drawn from Agabus rufipes Aubé: 
Prothorax very finely margined. Middle coxee rather closely approximate ; im- 
pression on the apex of intra-coxal process of the metasternum short and indefinite. 
Hind femora rather stout, with well marked lamina at extremity, without acumu- 
lated setee near this angle; hind tarsi rather elongate and slender, terminated by 
two rather small nearly straight and equal claws. Male front tarsi strongly 
compressed. Sculpture of the upper surface consisting of short impressed straight 
lines. 
In this species the basal joint of the hind tarsus is feebly lobed externally, and 
the following joints are destitute of lobing. While in Agabus leprieuri (No. 898) 
and Aglymbus sculpturatus, the four basal joints are strongly lobed ; and in these 
two species the male tarsi are nearly simple, and the sculpture of the upper surface 
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