908 On Aquatic Carnivorous Coleoptera or DytiscidcB. 



for fully half the length of the tibia, and is parallel or subparallel to its outer 

 border. 



The intermediate femora bear quite short setffi. The terminal abdominal stigmata 

 are of moderate size. The male front tarsi have the three basal joints dilated into 

 a circular plate ; this bears large palettes beneath, and of these the three or four 

 basal ones are distinctly but not greatly, larger than the others ; the basal fringing 

 hairs are present (except in one or two species) ; the middle tarsi have the three 

 basal joints distinctly, or even broadly dilated, and bearing beneath distinct 

 round palettes ; when the females have a sexual sculpture, it consists of some ruges 

 on each side of the thorax ; these rugse may be coarse and sparse, or very fine and 

 indistinct and dense. 



The species are distributed over the warmer parts of the Old and New Worlds 

 and Australia, and one group of a few species is peculiar to the northern or tem- 

 perate parts of Europe and North America, with the exception of one of its species 

 which occurs in Australia. 



f. 69.— Genus ACILIUS. ( Vide p. 672.) 

 Six species are united to form this rather heterogeneous aggregate. The form is 

 rather flat above, and the outline continuous, the surface is punctate above and 

 below, the head and prothorax being however in some species smooth. The pro- 

 thorax is without any lateral margin. The prosternal j^rocess is variable, but is 

 never very elongate or acuminate at the apex ; the middle coxce are rather widely 

 separated, and the impression on the apex of the intei'-coxal process of the meta- 

 sternum is a broad, short, shallow, rounded dej)ression. The hind coxae are 

 extremely large, their front border is very arched, and the wing of the metasternum, 

 much curved and deflexed outside the coxa, is dilated a little before the termination, 

 its extreme apex being however somewhat acuminate. The coxal lines although 

 subobsolete can always be distinguished in the posterior part of their course, and 

 they there mark off a distinct supra-articular border, which is never very broad, 

 and always acuminate or attenuate at its termination behind. The coxal lobes are 

 rounded and short, and there exists only an obscure trace of the coxal notch. 

 The swimming legs are well developed, but not very incrassate, and are terminated 

 by two nearly straight claws of which the inner is about twice as long as the outer 

 one : the spurs of the tibice are distinctly emarginate at the apes. The epipleurai 

 are variable in their width, but are never very narrow at the shoulders. The front 

 and middle femora bear a few, elongate, rigid sette on their lower margin. The 

 terminal abdominal stigmata seem rather well developed. The sexual characters 

 are variable, but the front tarsi of the males are highly developed, and the plate 

 formed by the dilated three basal joints is surrounded with beautiful fringing hairs, 

 and bears beneath three large palettes (one of them very large, but the other two 



