84 HYDROPHILIDA. 
This species is closely allied to the European &. luridus; but the individuals are 
rather larger, the sculpture is not so coarse, and the legs are longer and more 
slender. The depth of the ground-colour, the amount of maculation on the elytra, and 
the size of the metallic marks on the thorax are apparently rather variable. 
11. Berosus merens. 
Brevis, convexus, capite thoraceque metallescentibus, dense fortiter punctatis, hoc anterius et ad margines 
laterales testaceo ; elytris fuscis, vix discrete maculatis, profunde subaqualiter striatis, striis dense punctatis, 
interstitiis fortiter, fere seriatim punctatis; antennarum basi, palpis pedibusque testaceis, tibiis tarsisque 
posterioribus et intermediis palporumque apice infuscatis. 
Long. 14, lat. 2 lin. 
Hab. Mexico, Oaxaca (Hoge); GuateMaLa, Guatemala city, 5000 feet (Champion). 
Head broad and short, of a dark metallic colour, coarsely and evenly punctate. 
Thorax very closely, evenly, and coarsely punctate; in greater part of metallic colour, 
but the sides and anterior margin yellow. Scutellum rather short, coarsely and deeply 
punctate. Elytra with deep striz occupied by closely placed punctures; the interstices 
with rather large and distinct punctures, placed near one another and almost regularly, 
so as to form a series on each interstice. The basal portion of the legs, and also the 
middle and posterior tarsi are infuscate yellow. The mesosternal lamina is large; and 
its anterior angle forms only a very minute prominence. The basal ventral segment 
is carinate ; and the fifth ventral segment has behind an emargination, the base of which 
is distinctly bidentate in the female, obscurely so in the male. The basal (apparent) 
joint of the front tarsus is distinctly dilated in the male. 
I am not acquainted with any near ally of this obscure little Berosus. 
HEMIOSUS. 
Palpi maxillares parum elongati. Corpus subtus cum femoribus omnibus densissime subtilissimeque vix 
visibiliter pubescens, sericeo-opacum. Lamina mesosternalis magna, facie inferiore dilatata, anguste rhom- 
boidali. Suture ventrales profunde. Cetera fere ut in genere Beroso. 
The little insect I have separated because of the above characters has the appearance 
of a small compact short-legged Berosus ; but the peculiar silky opacity of the under 
surface is foreign to Berosus and the other Hydrobiini, and similar to what exists in 
Hydrochus; this pubescence extends over the femora, leaving only a small space at 
their extremity clear. The palpi are shorter than in any species of Berosus, and resemble 
those of Hydrochus. The antenne are 7-jointed ; joints first and second elongate, third 
much smaller, fourth small, lenticular ; joints fifth to seventh forming an elongate loosely 
articulated club. Under surface of head strongly compressed, carinate in the middle. 
Front coxe large, conical, exserted. Mesosternal lamina large, its lower face forming 
a narrow rhomboidal process, which is dull and pubescent, like the rest of the under 
surface. Middle of metasternum much detached, after the manner of Berosus, but to 
a still greater extent. Sutures between the ventral segments very deep, the first ventral 
