1855.] 357 



Antenna? 9-articulatre ; palpi omnes longiusculi Helnphorus. 



Antennas 7-articulata? ; palpi labiales breves Hydrochus. 



Palpi maxillares articulo ultimo brevi subulato Ochthebius. 



Palpi maxillarea longissimi Hydraraa. 

 Tarsi posteriores articulo 2ndo elongato, lmo brevissimo : 



III. Tarsi posteriores compressi ; metasternum postice spinosum (Hydrophilides.) 

 Prosternum minutum, sulcatum rlydrophilus. 

 Prosternum carinatum Hydrocharis. 



IV. Tarsi posteriores haud compressi ; metasternum simplex. (Hydrobides.) 



(Oculi duo ; abdomen segmentis ventralibua quinque). 



Tibia 1 et tarsi posteriores ciliati ; antenna 8-articulatae Berosus. 

 Tarsi posteriores breviter ciliati ; trochanteres postici 



magni ; antennas 8-articulate Laccobius. 



Tibiae et tarsi simplices ; trochanteres postici mediocres. 

 Palpi niaxillares elongati articulo ult. breviore ; an- 



tenna? 9-articulatae Philhydrus. 



Palpi maxillares art. ult. longiore : antennae 0- (raro 



8-) articulatas Hydrobius. 



V. Tarsi posteriores articulo lmo elongato (Sph.eridiides.) 



Antennae 9-articulata? ; metasternum antice productum Cyclonotum. 

 Antennae 8-articulatae ; 



mesosternum angustum ; prosternum carinatum Cercyon. 

 mesosternum pentagonum, dilatatum 



Prothorax marginatus Megalcsternum. 



Prothorax immarginatus Cryptopleururn. 



Helophorus Fabr. 

 (* Elytra stria Scutellaria nulla). 



1. H. oblong us, nigro-piceus, oblongus, capite thoraceque nitidis parce 

 punctulatis, hoc latitudiue sesqui breviore, lateribus late rotundatis, angulis 

 posticis obtusis, 5-sulcato, sulcis interraediis paulo undulatis, ad latera parce 

 granulato, elytris fusco-testaeeis, profunde punctato-striatis, pedibus testaceis. 

 Long. -23. 



Le Conte, Agassiz'Lake Superior, 217. 



Eagle Harbor, Lake Superior. Equals in size and form H. grandis, but is quite 

 different. 



2. H. lacustris, supra piceo-testaceus, oblongus, capite virescente. 

 thoraceque granulis depressis scabro, hoc latitudine fere duplo breviore, lateribus 

 antice rotundatis, pos:ice fere rectis, angulis posticis obtusis, 5-sulcato, sulcis 

 intermediis undatis, elyiris profunde punctato-striatis, subtus niger, pedibus tes- 

 taceis. Long. -18. 



Le Coate, Agassiz* Lake Superior, 217. 



E igle Harbor, Lake Superior. By a typographical eiror, the length is printed 

 23. 



3. H. ob s c u r u s, nigro-piceus, elongato-oblengus, supra obsolete aenescens, 

 thorace ad latera rotundata granulato, latitudine sesqui breviore, angulis posticis 

 obtusis, 5-sulcato, sulcis interraediis undatis, elytris grosse punctato-striatis, in- 

 terstitiis parce subtiliter punctulatis, pedibus testaceis. Long. 17. 



Le Conte, Annals of the Lyceum of Nat. Hist. New York, 5, 210. 

 San Francisco and Colorado River, California. 



4. H. n i t i d u 1 u s, elongatus, nigro-piceus, nitidus, thorace latitudine sesqui 

 breviore, lateribus late rotundatis, parce granul itis, angulis posticis obtusis, 

 5 sulcato, sulcis interraediis fere rectis, elytris fortiter punctato-striatis, interstitlis 

 subtilissime punctulatis, tibiis tarsisque testaceis femorious piceis. Long. -12. 



Eagle Harbor, Lake Superior, one specimen. 



5. H. linearis, elongatus, capite thoraceque aeneis,granulatis, hoc latitudine 

 sesqui breviore, lateribus fere rectis, aogulis posticis rectis, sulcis intermediis 



