324 On Aquatic Carnivorous Coleoptera or Dytiscida. 
basi medio elytrisque nigricantibus, his maculis magnis rufis ; prothorace subtiliter 
fere obsolete punctato; elytris crebre subtiliter, coxis crebre fortiter punctatis. 
Leng. 23, lat. 1§ m.m. 
The male differs from the female only by the considerable dilatation of the basal 
joint on the front and intermediate tarsi. 
The spots on the elytra sometimes nearly disappear, and it is then of a more 
or less unicolourous castaneous hue. 
This species a good deal resembles the European Hyphydrus cuspidatus 
(No. 180), but is really very distinct therefrom. It is rather broader, the thorax 
in the middle is longer, the surface is nearly opaque in both sexes, and the 
punctuation of the elytra is more even, being if anything rather finer at the suture 
than near the sides, whereas in Hyphydrus cuspidatus it is coarse near the suture 
but becomes quite obsolete towards the sides. In the male of the North American 
species the front tarsi are broader and flatter, (or less compressed laterally) than 
in the corresponding sex of the European species, and the dilatation of the basal 
joint of the front tarsus is a good deal greater. 
North America, (Michigan, Massachusetts). 147. 
187. Hydrovatus brevipes, n. sp.—Brevissimus, latus, convexus, piceus, sub- 
opacus, antennis pedibusque rufis ; elytris sat crebre et vix subtiliter, coxis crebre 
fortiter punctatis. Long. 24, lat. vix 12 m.m. 
The male is scarcely more shining than the female, but has the basal joints of 
the front and middle tarsi rather strongly dilated. 
This species is smaller, narrower and darker than Hyphydrus cuspidatus (No. 180), 
and the punctuation of the elytra is a little coarser, more sparing, and less evenly 
distributed : the structure of the tarsi proves it to be undoubtedly a distinct species, 
for they are considerably shorter in H. brevipes, and the joints are of a different 
shape. 
North America, (California). 148. 
188. Hydrovatus compressus, n. sp.—Brevissimus, latus, convexus, piceus, sub- 
opacus, capite prothoraceque rufescentibus, antennis pedibusque rufis, elytris sat 
crebre subtiliter, coxis posterioribus crebre fortiter punctatis. Long. 23, lat. 12 m.m. 
This species is extremely closely allied to Hydrovatus brevipes, and is per- 
haps scarcely distinct therefrom, the punctuation of the upper surface however 
is finer, and the thorax is longer in the middle, so that it forms a more marked 
and distinct angle over the scutellum. I have seen only two males ; the tarsi im 
that sex differ but little from those of H. brevipes, but the front ones are scarcely 
so short and broad. 
North America, (New Orleans). 149. 
