672 On Aquatic Carnivorous Coleoptera or Dytiscide. 
Dytiscus vittatus. I have seen but few specimens, and it is quite possible that 
ultimately the two supposed species may prove not to be distinct. 
Madagascar, and Portuguese Guinea. 1045. 
1051. Hydaticus petitu, Aubé, M.C.—Oblongo-ovalis, sat latus, niger, capite 
anterius prothoraceque ad latera testaceis, elytris vitta elongata laterali testacea ; 
antennis pedibusque anterioribus testaceis, tibiis intermediis piceis, pedibus pos- 
terioribus piceo-nigris. Long. 16, lat. 9 m.m. 
I see nothing to distinguish this species from H. exclamationis except the larger 
size, and more oblong form. It appears, moreover, to be variable, the yellow band 
of the elytra being sometimes very broad and conspicuous, and in other cases much 
reduced ; the colour of the undersurface and the legs also varies in depth. The 
largest individual I have seen is from Madagascar, while the smallest—the one in 
which at the same time the yellow band is most reduced—is from South Africa. 
Madagascar, Abyssinia, South Africa. 1046. 
II. 14.—Group THERMONECTINI. 
Episternal suture distinctly curvilinear; spurs of hind tibize minutely emargin- 
ate at the apex. 
The six genera constituting this group may be readily identified by the following 
abbreviated characters :— : 
Elytra closely punctate (in the other members of this group the elytra are im- ACILIUS. 
punctate, except occasionally there is a sexual sculpture in the female. (Vide below.) 
Coxal lines distinct; supra-articular border broad; middle femora with THERMONECTES. 
elongate sete. (Vide p. 677.) 
Coxal lines distinct; supra-articular border broad; middle femora with GTHIONECTES. 
short sete ; prosternum strongly elevate-compressed along the middle. (Vide p. 684.) 
Coxal lines obliterated so that no supra-articular border is present ; middle SANDRACOTTUS. 
femora with moderately long setee. (Vide p. 685.) 
Coxal lines obliterated so that no supra-articular border is present ; middle RHANTATICUS. 
femora with quite short spines. (Vide p. 691.) 
Coxal lines fine but yet distinct ; supra-articular border moderately broad ; GRAPHODERES. 
middle femora with rather short stout sete. (Vide p. 692.) 
I. 69.—Genus ACILIUS. 
Elytra punctate ; coxal border distinct, but not very broad. 
The six species of this genus are peculiar to Europe and North America. 
