&82 On Aquatic Carnivorous Coleoptera or Dytiscide. 
punctate ; metasternal groove imperfect; swimming legs elongate, slender and 
feeble ; hind coxze rather small, but wings of the metasternum not large. 
I am obliged to place these species isolated from the other groups ; the imperfect 
structure should place them near to group 1, and to Agabus hypomelas, (the 
first species of group 2) but the anterior claws of the male are elongate; while 
by the rounded sides of the thorax they approach the twelfth group, from which 
they differ by the scarcely compressed prosternal process, and the less obscure 
metasternal groove. 
Group 12. 
Prosternal process small, much compressed ; middle legs very approximate so 
that the metasternal groove between them is rudimentary and obscure. Sides of 
thorax rounded. Coxal lines rather deep and a good deal divergent in front. 
These four species seem to form a natural group on account of the above peculi- 
arities ; the hind coxe are short and their upper border but little arched, and the 
wings of the metasternum are not short, though in this respect the species do not 
closely agree inter se. The swimming legs are long and feeble. 
Agabus altaicus, Gebl., of the nineteenth group has a quite similar form of the 
prosternal process and metasternal groove, but the coxal lines are very different. 
Group 13. 
Prosternal process acutely raised or carinate along the middle, but its sides little 
depressed, so that it is not compressed, the sides evenly and distinctly margined ; 
metasternal groove well developed ; swimming legs elongate, rather slender; wings 
of metasternum large (D. confinis) or moderate (Agabus infuscatus); male front 
tarsi little incrassate, their claws elongate. 
These two species are readily distinguished from all others by the acutely carinate 
prosternal process. . 
Grovp 14. 
Hind coxe large, with acutely arched upper border; wings of the metasternum 
very short; prosternal process rather small; swimming legs rather slender. Male 
tarsi but little incrassate. 
These two species are associated together because of the very short wings to the 
metasternum ; in some other respects they are very different, Dytiscus femoralis 
has a very small prosternal process which is much compressed, and an extremely 
narrow mnetasternal groove ; Dytiscus abbreviatus has a moderately large prosternal 
process, and it 1s not compressed, but is somewhat carinate along the middle, and 
its metasternal groove is better developed. 
Group 15, 
Sides of thorax very feebly margined, not at all curved. Prosternal process very 
flat, not visibly margined ; metasternal groove rather elongate; wings of metasternum 
