HYDRGPORUS DAVISII. 
Order Coleoptera. Fam. Dyticidse Leach . 
Type of the Genus , Dytiscus depressus Fab. 
Hydroporus Clair., Sam., Ste., Curtis's Guide, Gen. 91. — Hyphydrus 
III., Gyll. — Dytiscus Linn., Fab., &c. 
Antenncs inserted before the eyes, longer than the thorax, filiform, 
1 1 -jointed, basal joint the longest, 2nd longer than the 3rd $ the 
remainder subclavate, nearly of equal length, the terminal joint 
a little longer and truncated obliquely (6). 
Labrum very broad and short, somewhat transverse -elliptic, the 
anterior margin deeply emarginate and ciliated at the centre (1). 
Mandibles semicylindric at the apex, one truncated obliquely at 
the apex, the other more bifid, both having a minute tooth on the 
inside near the middle (2). 
Maxilla bent and very acute, ciliated internally with long spiny 
bristles. Palpi, internal long and slender, biarticulate, the basal 
joint very short ; external long and robust, 4-jointed, 1 st and 2nd 
joints short, 3rd longer, 4th the longest and stoutest, ventricose, 
terminated by a vesicle (3). 
Mentum semicircular, deeply concave before with the centre 
slightly produced. 
Labium subquadrate, anterior margin slightly undulated. Palpi 
attached to large moveable scapes, triarticulate, basal joint short 
curved, 2nd longer slightly thickening to the apex, 3rd large 
ventricose truncated obliquely (4). 
Head broad, short, semiorbicular . Eyes small and remote. Thorax 
transverse, broadest at the bass, concave before , convex behind, the 
sides generally rounded . Scutellum none. Elytra broader than the 
thorax somewhat oval, truncated at the base, more or less pointed at 
the apex. Wings ample. Legs short , excepting the hinder pair which 
are formed for swimming. Thighs rather stout. Tibiae simple. Tarsi; 
4 anterior 4-jointed ( the penultimate joint being evanescent) , dilated 
in the males and cushioned beneath (5) ; hinder pair slender, 5- 
jointed. Claws simple equal . 
Davisii Curtis. — borealis ? Gyll. 4. p. 386. 8-9. 
Ochre colour, shagreened and sparingly punctured : antennae 
with the tips of the terminal joints and of the palpi black : head 
ferruginous at the base, with two black curved lines reaching to 
the eyes : thorax with a channel on each side and a slight point 
in the centre, with 2 black triangular spots below’ the middle, 
the anterior margin sometimes black : elytra rather strongly 
punctured towards the apex which is acuminated, straw 7 coloured 
at the base with 6 rather broad black lines on each, not reaching 
the base and several of them united towards the apex, the 3 first 
suffused and forming a blot towards the middle ; on the side are 
2 abbreviated and interrupted black lines forming 1 or 2 black 
spots : tips of the tarsal joints brown or black especially in the 
hinder pair : underside black. 
In the Cabinets of Mr. Davis and the Author. 
