1855.] 369 



1. H. 1 i n e a t u s, ater ovalis (femina utrinque obtusa) convexus, subtile 

 puoctulatus, capite thoraceque ad latera punctis perpaucis grossis notatis, hoc 

 fovea utrinque obliqua antica discoidali impressa, elytris tenuiter, obsolete 

 punctato-striati3 punctisque grossis seriebus 4 irregularibu3 notatis, palpis 

 rufo-piceis, fetnoribus intermediis grosse punctatis. Long. -Co. 



One female, San Diego, California. The club of the antennae is regular in form. 



2. H. obtusatus, ater (femina ovalis utrinque obtusa, mas elongato-ovalis) 

 convexus, subtile punctulatus, capite thoraceque ad latera punctis perpaucis 

 grossis notatis, hoc lineola utrinque obliqua antica discoidali impressa, elytris 

 obsolete tenuiter puactato-Striatis, punctisque sat magnis seriebus 4 impressis, 

 palpis rufis, fetnoribus intermediis subtiliter punctatis. Long. -55 -G2. 



Hydrophilus obtusatus Say, Journ. Acad. Nat. Sc. 3, 200 ( 9 ) 

 Hydrophilus as/us Say, Bost. Jonrn. Nat. Hist. 1, 170. 



Middle and Southern States. The male is longer and less obtuse in form, 

 and has the club of the antennae irregular. 



Philhydrus Solier. 



This genus is not adopted by Ericbson, who considers it as merely a section of 

 Hydrobius : the very great differrnce however in the length and structure of the 

 maxillary palpi, as well as the general appearance of the insects, induce me to 

 believe tbat the separation is natural. 



It is otherwise with the genus Helochares (formerly Helophilus) of Mr. Mulsant : 

 it was separated from Philhydrus by the mesosternum being only very slightly 

 caiinate, and not furnished with the anterior compressed lamina seen in most 

 species. Yet in examining the species of both Hydrobius and Philhydrus, I find 

 such want of uniformity in the sternum, as to convince me tbat characters drawn 

 from tbat portion of the body must be regarded as specific, or at most sectional 

 in their value. On. these principles the native species may be thus arranged. 



A. Mesosternum simplex, vel vix carinatum. (Helochares, Muls.) 



a. Prosternum simplex Sp. 1 2 1 3. 



b. Prosternum medio carinatum ; Sp. 4. 



B. Mesosternum autice aUe carinatum. (Philhydrus, Muls.) 



c. Prosternum medio carinatum Sp. 5 8. 



d. Prosternum simplex 



a. mesosternum carina continua notatum Sp. 911. 



b. mesosternum carina antica laminiforma Sp. 12 13. 



a. 



1. P. rotundatus, subrotundatus convexus, ater nitidus dense punctulatus, 

 thorace lateribus anguste rufo-testaceis, elytris seriebus punctorum solitis dis- 

 tinctis, postice obsoletissime striatis, stria suturali profunda ad medium abbre- 

 viata, margine postico indeterminate piceo, palpis rufis tarsis piceo-rufis. 

 Long. -27. 



Hydrophilus rotundatus Say. Journ. Acad. Xat. Sc. 5, 188. 



Pennsylvania Dr. Melsheimer. Resembles in form Hydrobius globosus, but 

 besides the difference in the sculpture of the elytra, the thighs are pubescent, and 

 without lustre except at the tip. 



2. P fimbriatus, latior, ellipticus convexus piceo-niger nitidus, dense 

 punctulatus, thoracis lateribus anguste testaceis, elytris stria suturali ad medium 

 abbreviata, punctorum seriebus solitis parum distinctis, versus apicem obsolete 

 Striolatis, margine fimbriata rufo-picea, palpis tarsisque rufis. Long. -2. 



.Melsheimer, Proc. Acad. Nat. Sc. 2, 101. 

 Pennsylvania and New York ; not rare. 



3. P. 1 a c u s t r i s, longior, ellipticus convexus, supra piceus, nitidus subtT 

 puncta,tus, palpis, capite macula utrinque antica testaceis, thoracis et elytrorum 

 lateribus indeterminate piceo-testaceis, his stria suturali antice abbrevhita. postice 

 p ; .ceo fimbriates ; sabtus niger, fetnoribus piccis, tibiis tarsisque rufo-piceis- 

 Long. -15. 



