886 On Aquatic Carnivorous Coleoptera or Dytiscide. 
genus Ilybius: moreover D. serricornis has the structure of the wing-cases similar 
to that which exists in Ilybius; on their inner face the marginal line is scarcely to 
be detected, but at the apex it is replaced by a tomentose area (this not so largely 
developed however as in Ilybius) ; whether this character exists in the other species 
of the group I am unable to say. The approximate coxal lines and the consequent 
form of the coxal lobes are somewhat similar to what is found in Copelatus, to 
which aggregate however this group shows no other approach, indeed it is more 
distinct therefrom than is any other group of the genus. 
Group 23. 
Under-wings reduced to subclavate slips, which are insufficient for flight ; 
sculpture of elytra consisting of isolated scratches, of which the basal ones assume 
an oblique, the outer and apical ones a transverse direction. 
The reduction of the wings is most remarkable and has but few parallels in the 
rest of the carnivorous water-beetles ; I have examined a specimen of each sex, for 
in the individual where I first observed the fact 1 thought the occurrence of so 
abnormal a structure must have been a mere deformity. Except for this character, 
and the absence of a coxal file, the species would come very near to group 8 by 
most of its other characters. 
I. 47.—Genus JILYBIOSOMA. (Vide p. 537.) 
This is an autogenus ; the insect is of the size of the larger Agabi, of dark colour, 
and with convex upper surface, so as to approach somewhat in form to Iybius. 
The outline of thorax and elytra is continuous ; the lateral margin of the thorax 
is broad and subobsolete, being but little raised, and at the posterior angles nearly 
effaced. The prosternal process is elongate, convex transversely but not compressed, 
its side finely margined, the margin not extending to the extremity. The coxal 
processes are largely developed in the transverse direction, and much separated 
from one another ; the coxal border is narrow, the coxal lines are a good deal diver- 
gent in their anterior portion, but they are abbreviated before reaching the front 
border of the coxa. The short stout hinder tarsi have a slight lobing of the 
hinder margins of the basal joints on the outer side. Hind coxee largely developed, 
with greatly arched upper border ; the short wings of metasternum greatly deflexed 
in consequence; swimming legs thick and abbreviated; epipleuree behind the 
middle narrow. 
Agabus regularis, Lec., which possesses the above characters has much the appear- 
ance of the large species of the 19th group of Agabus ; bui the linear form of the wings 
of the metasternum is much more conspicuous, and the swimming legs are thickened 
and abbreviated. It perhaps is less widely separated from Agabus politus and A. 
gagates, than it is from any other species known to me. Itinhabits North America. 
