940 On Aquatic Carnivorous Coleoptera or Dytiscide. 
I]. 14.—Group Tuermonscrini. (Vide p. 672.) 
This aggregate of the second degree consists of forty-one species arranged in 
four aggregates, and of two autogenera. The size of the individual is not less than 
one-third and scarcely exceeds two-thirds of an inch of length ; the surface is nearly 
always variegate,and may be punctate though it is generally very smooth and polished. 
The antennal portion of the head is short, sometimes extremely short, and the eyes 
are large. The thorax is destitute of a lateral margin; the prosternal process 1s 
short and obtuse or rounded at the apex, and is received into a broad, short, 
shallow impression on the apex of the inter-coxal process of the metasternum, the 
middle coxe being always somewhat widely separated. The hind cox are 
extremely large, their upper border is greatly arched, and never separated by a 
long space from the middle coxze, and often very closely approximated thereto ; 
the metasternum very elongate in the middle, terminates on each side as a slender 
side wing deflexed for a considerable distance outside the coxa, the band so 
formed is a little broader just before its termination than it is a little distance in 
front of that point; the suture between the wing of the metasternum and the 
episternum (that is the piece at the outer anterior part of the breast) is very 
distinctly curvilinear; and the most internal portion of the metathoracic 
epimeron may frequently be distinguished, even when the wing cases are quite 
closed, as a small angular piece, whose inner angle nearly touches the terminal 
angle of the side wing of the metasternum behind the apex of the episternum : as 
however the sutures between this epimeron and the adjoining pieces are very 
obliterated, it easily escapes observation even when really exposed. 
The coxal lines are always small, and sometimes quite obliterated, and even when 
most developed their anterior part is always very far indeed from attaining the 
anterior border of the coxa; the supra-articular border when it can be distinguished 
ig never very narrow, and is frequently so broad that it forms nearly one half of the 
coxal lobe. The swimming legs are always highlv developed; the upper face of 
their femora is either smooth and polished, without any punctuation, or possesses 
some isolated punctures placed in a transverse manner on the basal portion and 
without any development of pubescence: the upper face of the tibia bears a short 
series of contiguous punctures (4 to 7 in number) placed near the middle of the 
limb in a transverse or obliquely transverse direction, each puncture bears a thick 
seta or spine bifid at the extremity ; the tibia bears at the apex two rather siender 
spurs, each of which when viewed in a certain direction is seen to have its apex not 
quite pointed but more or less minutely emarginate, though viewed in another 
direction the spur may appear quite acuminate. 
The aggregate is a perfectly natural one, distinguished by the form of the epi- 
sternal suture and the bifid extremity of the posterior tibial spurs; its curved epi- 
sternal suture is present in the adjoiming Eretes, but the bifid extremity of the 
