522 On Aquatic Carnivorous Coleoptera or Dytiscidce. 



728. Dytiscus elongatus, GjW., Acjahus elongotiis,M. C. — Oblongo-ovali.s,angustulus, 

 niger, supra fusco-subseneus, antennis pedibusque testaceis, femoribus plus 

 minusve infuscatis ; elytris omnino densissime subtilissimeque reticulatis, sat 

 nitidis ; prothorace lateribus baud cui'vatis, margine laterali subtili. Long. 7, lat. 

 3j m.m. 



In the male the front tarsi are peculiar in form, the basal joint is a little thickened 

 at its extremity, but the hairs on it and the following two joints are very little 

 indeed, the fifth joint is elongate, and is underneath incrassate about the middle, 

 the claws are elongate, and at the base abruptly bent, especially the hinder one, 

 they are without tooth, but are a little sinuate. The intermediate tarsi have the 

 basal joint a good deal thickened, it and the two following ones bearing a few 

 extremely short and indistinct glandular hairs. There is no difference in the 

 sculpture of the sexes. 



The antennae of this species have a peculiarity, (pointed out by C. J. Thomson) 

 which is not however very conspicuous ; they have the 6th to 9th joints a little 

 thickened at the extremity at the lower angle ; this is more conspicuous in the 

 male than it is in the female, and the prominent spot in the former sex seems to 

 be a fovea filled with a glandular pubescence. 



Northeni Europe ; (Sweden, and Finland to 64°, according to Sahlberg). 765. 



Group 16. 



Prosternal process compressed on its apical half or through its whole length, 

 finely but quite distinctly margined ; wings of metasternum large, or moderately 

 large ; swimming legs moderately short ; reticulation of upper surface frequently 

 very conspicuous ; male front tarsi much incrassate and dilated, their claws various, 

 either short and dentate beneath, or elongate, or very elongate. 



Seven species, six of them North American, and one North European. 



729. Agabus reticulatus, Aube, Spec. p. 355. — Ovalis, sat convexus, niger, 

 elytris fuscis vel fusco-nigris, limbo externo rufescente, prothorace ad latera anguste 

 minus distincte rufescente, antennis pedibusque rufis, posterioribus piceis ; supra 

 undique evidenter reticulatus, vel sat nitidus (cj) et reticulis .sat magais, vel sub- 

 opacus (?) et reticulis baud magnis. Long. 8, lat. 41 m.m. 



The male has the basal joints of the Iront and middle tarsi a great deal incrassate, 

 and broadly furnished beneath witli hairs ol' which the terminal half bear three 



