70 HYDROPHILIDZ. 
carination. The mesosternal elevation does not form any angle, but displays only a 
gentle curve. 
The two individuals before me, agreeing in these structural characters, are discrepant 
in size, the smaller variety being only 1% lin. long, and being rather paler in colour and 
a little more finely punctate. 
7. Philydrus ochraceus. 
Philhydrus ochraceus, Melsh. Proc. Ac. Phil. ii. p. 101°; Lee. op. cit. 1855, p. 3717; Horn, Trans. 
Am. Phil. Soc. 18738, p. 129°. 
Hab. Norra America1, from Massachusetts to Florida? ?.—Mxrxico; GUATEMALA, 
Duefias, Paso Antonio (Champion). 
The specimens from Guatemala appear to form a variety in which the punctuation of 
the upper surface is diminished, and there is an indistinct stripe of dark colour along 
the suture. As P. ochraceus is variable in respect of its sculpture, and as the Guatemalan 
individuals quite agree with it in structure, they cannot be looked on as a distinct species. 
The resemblance to those varieties of P. equalis that have a slight punctuation on the 
wing-cases is very great; but the slight development of the mesosternal carina in 
P. ochraceus is quite sufficient to validate its specific distinction. The species appears 
to be variable even in Guatemala; for the two specimens from Paso Antonio have the 
wing-cases almost without punctuation, and wanting the obscure stripe of dark colour 
existing in the more numerous specimens from Duefias. 
HYDROCOMBUS. 
Genus Philhydri affine, sed tarsi posteriores quadriarticulati, mesosternum ante coxas lamina transversa armatum, 
pronotum basi immarginatum palporumque maxillorum articulus pseudo-basalis aliter arcuatus. 
Palpi maxillares quadriarticulati, articulo basali brevissimo fere nullo, secundo margine anteriore haud convexo 
sed subconcavo, tertio quam secundus breviore sed quam articulus quartus longiore. Palpi labiales 
perbreves. Mesosternum lamina transversa paulo ante coxas intermedias plus minusve elevata armatum. 
Tarsi anteriores quinquearticulati, intermedii et posteriores quadriarticulati, hi articulo basali elongato, 
quam secundus duplo longiore; ungues simplices, tenues, leviter arcuati. Elytra punctata, striaque 
suturali impressa. 
This genus has some species in North America; but they have not yet been distin- 
guished from Philydrus, though the genus is a remarkably distinct one and is well 
defined by its structural characters ; all the species, however, have very much the external 
appearance or facies of Philydrus. Hydrocombus is quite distinct from the genus 
just mentioned, as well as from Helochares, by the truly four-jointed middle and 
hinder tarsi: this character is not illusory; for even when the tarsi are mounted in 
Canada balsam no trace of a division of the basal joint can be perceived. Hydrocombus 
has this peculiar character in common with the European genus Cymbiodyta, Bedel ; 
and the two genera also agree in that they have the pseudo-basal joint of the maxillary 
