910 On Aquatic Carnivorous Coleoptera or Dytiscide. 
mark off a broad supra-articular border: the spurs of the hind tibize are quite 
distinctly emarginate at the apex, and the tarsi are terminated by two straight 
claws of very unequal lengths. The epipleuree are narrow, even at the shoulders. 
The intermediate femora and tibiz bear long setee on their hinder or inner margin, 
and the three basal joints of the middle tarsi bear each below, at the inner and outer 
edge (in each sex), a single elongate depressable or erectile seta: the middle tibiz 
are slender and always without spinules on their lower face; the front tarsi in the 
female bear long, rigid, erect sete. The apical abdominal stigmata are quite small. 
The male front tarsi have their circular plate furnished heneath with numerous 
small palettes, and at the base with three of larger or variable size: the intermediate 
tarsi are quite simple. The fringing hairs around the front tarsi are very little 
developed, but this is variable, for they are better developed in Acilius basilaris 
than in the other species. 
The females show a sexual sculpture on the basal portion of the wing-cases, 
consisting of rather elongate punctures ; in some species this sculpture extends on 
to the sides of the thorax. 
The genus is peculiar to the warmer pirts of the New World, one or two species 
extending to the southern parts of the United States of North America ; numerous 
species besides those described doubtless exist. 
Thermonectes simulator is a very peculiar species, entirely resembling in form 
and markings the species of the European genus Graphoderes. 
I. 71.—Genus @THIONECTES. (Vide p. 684.) 
The unique species is hnown to me by two individuals only; and its general 
characters appear to be those of Thermonectes, but the front and middle tarsi bear 
beneath only short rigid sete, in place of the elongate ones of Thermonectes, and the 
middle femora have only some short sete. 
The prosternum is very thickened along the middle, and the front legs are rather 
broadly separated, so that although the prosternal process is broad it is not broader 
than the prosterntm between the legs: the hind legs are well developed for 
swimming, and are terminated by two claws of which the outer is much more slender 
than the other, but is not much shorter. 
In all the other characters I can observe, the species agrees with Thermonectes. 
This insect occurs in West Africa; the species of Thermonectes only in the New 
World. 
I. 72—Genus SANDRACOTTUS. (Vide p. 685.) 
Ten species, of rather large size ($ to # inch of length), rather convex form, highly 
polished surface, and beautifully variegate colour, are united to form this aggregate. 
The antenral portion (7.e., portion anterior to a transverse line drawn across the 
