On Aquatic Carnivorous Coleoptera or Dytiscide. 683 
1069. Colymbetes marmoratus, Hope, l7ydaticus marmoratus, M.C.—Convexius- 
culus, leevigatus, nitidus, subtus rufus, supra niger, lete testaceo-variegatus, elytris 
maculis magnis testaceis ; elytris epipleuris haud latis. Long. 13, lat. 73 m.m. 
Fem., elytris ad basin punctis elongatis numerosis impressis. 
In the male of this species the three larger palettes on the undersurface of the 
front feet differ little inter se in size, and are distinctly, but not greatly, larger 
than the others. The species is a very prettily coloured one and easily distinguished 
amongst its allies by its colour and markings ; the sides of the thorax are broadly 
yellow, and across the middle is a yellow band which however does not communicate 
with the yellow of the side: the side margin of the wing case is yellow till near 
the apex, at the base on each side of the scutellum is a roundish yellow spot, and 
between this and the humeral angle an irregularly shaped yellow mark, between 
these two basal marks are three small spots arranged in a longitudinal direction, 
the anterior of them being so small as to be a mere speck; half way towards 
the extremity the largest spot exists, 1t is placed near the suture, and external to 
it and a little more backward there is another large yellow spot connected with the 
yellow lateral margin, there are two other spots near the suture behind the large 
yellow spot, and there are also three other spots, besides the one already mentioned, 
communicating with the yellow lateral margin; there are in all eleven spots on 
each wing case, without counting the very minute basal speck above described 
which is very frequently absent. 
Mexico. 972. 
1070. Acilius margineguttatus, Aubé, M.C.—Minor, subtus convexiusculus, 
nitidus, niger, capite anterius et in medio verticis, prothorace ad latera et trans- 
versim in medio, elytris signatura humerali maculisque duabus ad latera 
(interdum etiam cum vitta transversa sub-basali, aliaque subapicali), antennis 
pedibusque anterioribus testaceis; pedibus posterioribus nigricantibus femoribus 
ad apicem pallidis ; epipleuris angustulis. Long. 9, lat. 5 m.m. 
Fem., elytris ad basin lineolis brevibus, plus minusve numerosis, impressis. 
In the male the three larger palettes of the front tarsi, are well developed, 
and subequal inter se, in size. The species is a variable one in size, in colour, and 
the sexual sculpture of the female. The yellow mark across the middle of the 
thorax is sometimes nearly absent. The yellow mark on the shoulder of the wing 
case is always present and there is generally a transverse mark proceeding from its 
hinder part towards the scutellum, according to the extent of its development it 
has the appearance either of a spot or spots, or a nearly entire vitta: there is a 
yellow spot at the side about the middle, and this although variable in size is 
never largely developed ; there is another spot at the side near the extremity, and. 
this is sometimes developed into a subapical fascia ; near to the suture at the apex 
TRANS. ROY. DUB. SOC., N.S., VOL. I. 4T 
