On Aquatic Carnivorous Coleoptera or Dytiscide. 873 
scutellum is quite exposed, and visible at the base of the elytra, the base of the 
prothorax being but little prolonged and not at all acuminate in the middle. The 
front and middle tarsi are conspicuously five-jointed, the three basal joints being 
moderately broad (subject however to sexual difference in this respect), the third 
being emarginate at the apex but scarcely bilobed; the fourth joint although 
perfectly distinct is much smaller than the others, and the fifth is rather elongate. 
‘The prosternum is subvertical in direction between the coxe, and is not in the least 
thickened, or raised, along the middle ; its process is large, conspicuously margined, 
pointed at the extremity, which is received into a deep fossa on the apex of the 
inter-coxal process of the metasternum. The central fork of the mesosternum is 
unperfectly connected with the metasternum. The hind coxe are of moderate size, 
about as elongate along the mesial line as near the side, but their front border is. 
a good deal extended in the anterior direction. ‘The hind coxal cavities are nearly 
but not quite contiguous, and the coxal processes form divergent lobes, which have 
however but little extension in the longitudinal direction. The swimming legs. 
are quite slender, their tibiz and tarsi being slender and elongate, the latter 
terminated by two equal curved claws. The wing-cases are acuminate at the 
extremity, and the body terminates in a projecting mucro. 
These insects have the prosternum of the Hydroporini, but no Hydroporini show 
a conspicuous scutellum, and very few have distinctly five-jointed front and middle 
tarsi. Thus the aggregate formed by these few species, though it may be classed 
in the tribe Hydroporides, cannot be placed in any of the groups forming the tribe, 
and so must remain an isolated genus. ‘These insects are so rare, that I have not 
been able to obtain any specimen for dissection. 
I cannot suggest any valid approximation to other insects, but there may be a 
slight approach to the North American Hydroporus oblitus, Aubé, and Hydroporus 
collaris, Lec., for these imsects have the apex of the scutellum distinctly exposed, 
and the prosternal process and hind coxal cavities are not very dissimilar to what 
we find in Celina. 
The species of Celina are found only in Southern and Central America, with two 
rare species in the United States of North America. 
I. 48.—Genus METHLES. (Vide p. 489.) 
This isolated genus at present consists of three species, they are small Hydro- 
poroid insects, but with the apex of the elytra, and extremity of the body spinose 
and acuminate. 
The scutellum is quite concealed, the base of the thorax distinctly accuminate in 
the middle: front and middle tarsi five-jointed, cylindric, the basal four joints sub- 
equal, without clothing beneath. Prosternum between the front coxz very small, 
forming a very slender depressed band placed only at a very obtuse angle from the 
