On Aquatic Carnivorous Coleoptera or Dytiscide. 639 
marginato, sed margine basali angusto; elytris margine flavo ad apicem lato sed 
per-obsoleto, antennis pedibusque rufis, tibiis tarsisque posterioribus obscurioribus ; 
pedibus posterioribus haud brevibus ; prosterni processu sat lato ; coxarum process- 
-ubus obtusis. Long. 30, lat. 15 m.im. 
Alas, elytris ad apicem parum punctatis. 
Fem. (a), elytris ad basin paulo ultra medium sulcatis, apice sat crebre punctatis ; 
prothorace crebrius punctato. 
(b), Sat nitida, elytris haud 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. marginalis. 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 species. 
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 elongato, acuminato ; coxarum processubus obtusis. Long. 
35, lat. 18mm. (Long. 31-387 m.m.) 
Mas, elytris ad apicem sat crebre punctatis. 
Fem., 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 ailied 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 |and 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 
