On Aqimtic Carnivorous Coleoptera or Dytiscidcs. 639 



marginato, sed margine basali angnsto ; elytris margine flavo ad apicem lato sed 

 per-obsoleto, antennis pedibusque rufis, tibiis tarsisque posterioribus obscurioribus ; 

 pedibus posterioribus baud brevibus ; prosterni processu sat lato ; coxarum process- 

 ubiis obtusis. Long. 30, lat. 15 m.tn. 

 .1/as, elytris ad apicem parum puuctatis. 



Fern. («), elytris ad basin paulo ultra medium sulcatis, apice sat crebre punctatis ; 

 prothorace crebrius punctato. 



(h), Sat nitida, elytris baud sulcatis, ad apicem parcius punctatis, prothorace ad 

 latera subtiliter punctato. 



In the male the small palettes on the front feet are moderately developed, while 

 those on the middle feet are quite small. 



The species is rather more elongate than D. fasciventris, and may be readily 

 distinguished therefrom by the less punctuation of the apical half of the elytra, 

 by the front and hind margins of the thorax being more distinctly bordered with 

 yellow, and by the absence of black markings on the ventral segments, as well as 

 by several other minor characters. It is about intermediate between D. fasciventris 

 and D. margi.ialis. The yellow basal margin of the thorax is moderately broad in 

 front of the scutellum, but towards the sides is excessively narrow. I have seen 

 only two pairs that I can refer to this species, and I feel not quite sure that they 

 may not represent two distinct sj^ecies. 



North America. 940. 



991. Dytiscus dimidiatus, Berg., M.C. — Major; anterius angustatus; nitidus, 

 subtus ferrugineus metasterno in medio picescente, supra niger, prothoracis 

 elytrorumque lateribus flavis. antennis pedibusque rufis, tarsis posterioribus nigris ; 

 prosterni processu sat elongate, acuminate ; coxarum processubus obtusis. Long. 

 35, lat. 18 m.m. (Long. 31-37 m.m.) 



Mas, elytris ad apicem sat crebre punctatis. 



Fein., sat nitida elytris ad basin vix ultra medium sulcatis, apice crebre punctatis, 

 prothorace intra marginem sat impresso, lateribus subtiliter punctatis. 



In the male the small palettes of the front tarsi are rather highly developed, 

 while those on the middle feet are quite small. 



This species is not closely allied to any other, but is about intermediate between 

 D. punctulatus and D. marginalis. There is a very narrow reddish band on the 

 front of the thorax, and sometimes a yellowish appearance in the front of the 

 scutellum, at the extremity of the wing-cases the yellow band is divided by a very 

 large patch of dark colour, and the anterior portion of the band is placed at a con- 

 siderable distance in front of the apex. The female is always sulcate, and the 

 interstices of the grooves are but little punctured. The species exhibits little 

 variation ; there is however a tendency in the females to a breaking up of the 



