280 
NORTH AMERICAN GYRINUS (cOLEOPTERa) 
Venlralis lias never been recog-nized with certainty from Kir- 
by’s veiy brief description, which applies about eiiually well to 
any one of a half dozen species occurring in the Northern United 
States and Canada. 
Through the courtesy of Messrs. Gahan and Arrow of the 
British iMuseuni, one of Kirliy’s two original specimens has 
lieen sent me for examination. The specimen is a male, for- 
tunately with the tip of the oedeagus visible, which enables 
UK' to fix its identity with absolute certainty. The veniralis 
of LeConte’s paper (18()8), and of Regimbart’s iMonograph is 
not Kirby’s species, but jiroves now to be an undescribed form 
for which the name lecontei is proposed in the present paper. 
liy the form of the apex of the median lobe of the oedeagus, 
ventralis may be instantly separated from every other species 
in our fauna; but to determine it from superficial characters 
alone is difficult or impossible even to the experienced student. 
The following are the species occupying in part the same terri- 
tory, with which it may be confused: lecontei, aquiris, conjinifi, 
hifariiis and fraternus. 
From lecontei and oqiiiris, vcntrolis — if not discoloi'ed — may 
in most cases be distinguished by its practically uniform tint 
of the pale under surface, the venter being almost invariably 
darker medially than around the margins in the two species 
named. Aquiris is also of somewhat narrower form, while 
lecontei is a rather larger and slightly more robust species. 
Confinis is slightly narrower, less convex, and with more easily 
detectable alutaceous sculpture, especially in the female. Bi- 
farius is extremely similar to ventr(tlis, but when closely com- 
l)ai'ed the lateral eleventh elytral stria is slightly farther from 
the mai'gin, and, as in conjinis, the alutaceous sculiiture is more 
evident . So far as I have observed there is no way of se])arating 
the pri'sent s})ecies from fraternus except by genitalic charac- 
ters. 
t. Gyrinus fraternus Coiiper 
'I'liis si)('ci(‘s was (h'scrilxMl in bSbr) by A’illiam Gouiier of 
(hiebec, who says it is common in ])onds lU'ar that city in .lime 
mid .Inly, d’lu'ri' ari' two supposi'dly typical sixa-imiuis from 
