526 On Aquatic Carnivorous Coleopiera or Dytiscida;. 



736. Dytiscus arcticus, Payk., Agahus arclirus, M.C. — Ovalis, angustulus, supra 

 minus convexus, minus nitidus, subtus nigricans, capite prosternoque ox parte 

 testaceis, supra fusculus, capite anterius, prothorace lateribus vittaque transversa 

 in medio, elytris lateribus, aiitennis pedibusque testaceis ; supra undique conspicue, 

 crebrius, irreguiariter reticulatus ; prothorace margine laterali persubtili. Long. 7, 

 lat. 3| m.m. 



The male has the front and middle tarsi much incrassate, and furnished beneath 

 with large quite circular palettes, which appear to be seated directly on the tarsus 

 and are about ten or twelve in number : the front claws are unequal, the posterior 

 one being rather elongate, and slender and sinuate beneath, while the anterior one 

 is rather shorter, and has the basal half thickened so as to form an angular pro- 

 jection beneath. The scratches on the upper surface are very deep in the female, 

 and in this sex there is generally, but not always, a peculiar sinuation of the sides 

 of the thorax just behind the front angles. 

 The colour varies somewhat. 



Northern Europe; Arctic Siberia; (North America, teste Crotch). Sweden; Finland to G9^ north, 

 Sahlberg ; Scotland ; Alsatia, (coll. Castlenau). 794. 



737. Dytiscus sturmi, Gyll., Agahus ■sturmi, M.C. — Ovalis, sat convexus, minus 

 nitidus, nigricans, supra fuscus, capite thoraceque subsenescentibus, hujus olytro- 

 rumque lateribus testaceis, antennis pedibusque testaceis, femoribus medio 

 nigricantibus ; supra undique subtiliter erebre reticulatus ; prothorace margine 

 laterali subtili. Long. 8, lat 42 m.m. 



The male has the front and middle tarsi a great deal incrassate, and furnished 

 beneath with large palettes which are about twelve in number ; the front claws are 

 rather elongate and of about one length and the anterior one is nearly straight 

 "beneath ; the apical joint of the middle tarsus is very elongate : there is no differ- 

 ence of sculpture in the sexes. 



The colour is subject to some variation. 



Europe ; (Sweden ; Finland to 63° North, Sahlberg ; Britain, France, Belgium, Germany). 795. 



Group 18. 



Swimr)iing legs highly developed, short and incrassate ; prosternal process rather 

 broad, but a good deal compressed; wings of metasternum moderately large ; male 

 front tarsi much incrassate, furnished beneath with rather long hairs, bearing rather 

 well developed palettes, claws rather short. 



One Japanese species. 



