On Aquatic Carnu-orous Coleoptera or Di/tiscicke. 841 



The ventral sutures are very deep, that between the second and third abdomuial 

 segments veiy deep even in the middle. 



The sexual distinctions are very slig-ht. The only species known has been found 

 in Cayenne. 



I. 13.— Genus DEROVATELLUS. {Vide p. 28G.) 



This is an autogenus ; the insect is of the size of an average Hydroporus, and 

 has much the appearance of the species of that genus ; the upper surface is densely 

 and rather finely punctured. The prosternal process is short and broad, rhomboidal 

 in form, with its extremity received between the middle coxiB ; these are exposed, 

 and contiguous. The mesosternum is placed at a slightly obtuse angle with the 

 metasternum, and is not much exposed : the coxal lines are a little divergent in 

 front, but not much separated, and are indeed approximate through their whole 

 length, they are however distinctly turned outwai'ds in their terminal portion ; the 

 coxal border has very little extension in the transverse direction. The posterior 

 trochanters are normal, as are also the ventral sutures, that between the second and 

 third segments being quite obliterated in the middle : the claws of the front tarsi 

 are excessively minute. The sexual distinctions are very slight. 



The insect inhabits tropical America. 



I. 1 4.— Gen us LA CCOPIilL US. ( Vide p. 2 8 7.) 



About eighty species compose this aggregate. They are insects of small size, the 

 largest attaining only 6 m.m. of length ; the upper surface is frequently moi'e or 

 less variegate, though generally in an indefinite manner, and its sculpture is either 

 slight, or wanting, giving place to a very polished surface, the underside is free 

 from sculpture except that there are elongate, oblique scratches on the ventral 

 segments ; the form varies from nearly elliptical to an oval, and is never very 

 convex, the outline is very continuous. 



The head is very short and broad, the portion in front of the eyes being extremely 

 short, the eyes of moderate size have their circular inner outline only very obscurely 

 infringed on at the insertion of the antennae : the head in front shows no trace 

 of a raised margin, its emarginate-truncate front edge being very thin and closely 

 applied to the exposed labrum. The antennse are slender and quite symmetrical, 

 showing no peculiar forms or sexual differences ; the parts of the mouth are small 

 and the palpi simple. The thorax is without any lateral mfirgin, and almost 

 without any punctures along the margins. The scutellum is quite concealed. The 

 prosternum is very small, the small, conical, front coxae being placed very near the 

 front, so that there is only a verj; short transverse band in front of them ; the 

 prosternal process is remarkably small, very acuminate, much compressed, and 

 frequently its apex is prolonged so as to form a very slender, elongate, excessively 



