324 On Aquatic Co.rnivoroiis Coleoplera or Dytiscidtr. 



Iiasi medio elytrisque nigricantibus, his maculis niagnis rufis ; prothorace subtiliter 

 fere obsolete punctato ; elytris crebre subtiliter, coxis crebre fortiter punctatis. 

 Long. 21, lat. ll 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. ISO), but is really very distinct therefrom. It is rather broader, the thorax 

 in the middle is longer, the surface is nearly ojiaque in both saxes, and the 

 punctuation of the elytra is more even, being if anything lather 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. 21, lat. vix H- 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. ISO), 

 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 difterent 

 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. 2j, lat. Ij 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 in 

 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. 



