On Aquatic Carnivorous Coleoptera or Dytiscide. 675 
the punctuation of the wing-cases is not so dense as in the typical individuals. 
These characters become more or less modified in Californian specimens, and in the 
broader and shorter individuals from this part of the Pacific district the resemblance 
in form to Dytiscus fraternus is very great, and is accompanied by a great extension 
of the black mark of the hind femora. A variety of this Californian race has, 
however, the undersurface and hind femora entirely yellow. 
Crotch states that a form of the female without grooved elytra occurs, but I have 
not seen such, the variation tending, when departure from the type is made, in the 
direction of greater extension of the grooves, and I suspect that the individuals 
alluded to by Crotch should have been rather referred to Dytiscus fraternus. 
The variations of the species, as given by Crotch, are -— 
Var. simplex, Lec. Posterior femora piceous, knees yellow; female with the 
elytra smooth. San Diego. 
Var. oregonensis. Elytra paler, more thinly irrorated with black, fascia paler and 
more distinct, posterior femora pale. Oregon. 
Var. latiusculus, Lec. Testaceous beneath, sulci of 9 as in type. 
Var. abbreviatus, Man., Aubé. Larger, femora testaceous, sulci in the female 
almost reaching the base. 
North America. Very widely distributed from Sitka to Haiti. 958. 
1055. Dytiscus fraternus, Harr., Acilius fraternus, M. C.—Supra parum 
convexus, testaceus, vertice prothoraceque signaturis transversis nigris, elytris 
creberrime nigro-irroratis fascia transversa pallida parum distincta, subtus pectore 
abdomineque nigris, hoc minus testaceo-variegato ; femoribus posterioribus nigri- 
cantibus : corpore creberrime punctato ; antennis elongatis, tenuissimis. Long. 14, 
lat. 8 m.m. 
Mas, subopacus, elytris creberrime punctatis. 
Frem., elytris sulcis latis, setulosis, ad basin valde abbreviatis, suturali paulo 
breviore. 
This species has the male characters the same as in Acilius semisulcatus, except 
that the three tufts of hairs on the intermediate tarsi are much less developed, and 
appear indeed on a hasty inspection to be entirely wanting. 
The species is very closely allied to A. semisulcatus, but the anterior border of 
the hind coxa is always separated by a longer space from the middle coxal cavity. 
Besides this the species is usually rather broader, darker in colour, and more densely 
punctured, and the furrows on the elytra of the female are more abbreviated in 
front. A variety of this latter sex occurs in which the elytra are, like those of the 
male, without grooves. 
The species varies somewhat in the colour of the upper surface, especially in the 
TRANS, ROY. DUB. SOC., N.S., VOL. II. 48S 
