372 [June, 



Middle and Southern States : the four internal striae of the elytra are gradually 

 shorter anteriorly: the sutural one is bifid by the confluence of a small scutellar 

 stria, but with the second is almost entirely obliterated on the anterior fifth of 

 the elytra. The anterior dilated plate of the mesosternum is not quadrilateral 

 as in the preceding, but triangular and acute as in Hydrobius, to some species of 

 which it bears considerable resemblance, but may be distinguished by the long 

 slender palpi. 



In Fauna Bor. Am. (p. 120) Mr. Kirby cites the European P. marginellus and 

 melanocephalus as occurring in North America : the descriptions however are 

 not sufficiently characteristic to enable them to be referred with certainty to any 

 of the species above described to whice they may belong. 



Hydrobius Leach. 

 A. Antennae 9-articulatae. 



1. H. t u m i d u s , rotundato-ovalis valde convexus, seneo-ater nitidus con- 

 fertim punctulatus, thorace lateribus parce punctato, elytris striis subtiliter punc- 

 tatis haud impressis, stria suturali profunda antice obliterata, interstitiis alter- 

 natim punctis maioribus uniseriatim notatis : mesosterno lamina magna trian- 

 gulari acuta antice perpendiculari armata. Long. -33. 



New York and Pennsylvania, rare. Not so globose as H. globosus, but 

 equally convex : the different form of the mesosternal protuberance will at once 

 distinguish it ; but in addition to that character, the prosternum at tip is armed 

 with a small acute tubercle. 



2. H. globosus, rotundatus valde convexus, seneo-ater nitidus confertim 

 punctulatus, thorace lateribus parce punctato, elytris striis subtiliter punctatis 

 haud impressis, stria suturali profunda antice obliterata, interstitiis alternatim 

 punctis maioribus U'>iseriatim notatis ; mesosterno tuberculo magno pyramidato 

 acuto armato. Long. -30. 



Hydrophilus globosus Say, Long's Expedition, 2, 276. 



New York and Pennsylvania. The protuberance of the mesosternum is thick 

 and pyramidal, with its posterior face flattened. 



3. H. insculptus, ovalis modice convexus, piceo-niger nitidus confertim 

 punctulatus, thorace latitudine plus sesqui latiore linea utrinque antica discoidea 

 punctisque paucis ad latera notato, elytris striis profundis punctatis, internis 

 antice subobsoletis, suturali antice bifida, interstitiis alternatim punctis maioribus 

 notatis ; mesosterno lamina triangulari acuta postice perpendiculari armato. 

 Long. -30. 



One specimen from New York. Less convex and more oval than the next, 

 which it closely resembles ; the larger size of the mesosternal protuberance will 

 distinguish it. The greatest breadth of the elytra is about two-fifths from the 

 tip. 



4. H. regularis, ellipticus convexus, piceo-niger nitidus confertim punc- 

 tulatus, thorace latitudine duplo breviore linea utrinque antica discoidea punc- 

 tisque paucis ad latera notato, elytris striis punctatis, internis antice subobso- 

 letis, suturali antice bifida, interstitiis alternatim punctis maioribus notatis ; 

 mesosterno antice subcarinato, mucrone parvo subacuto ad medium armato, 

 Long. -34. 



Vermont, Prof. Adams. 



5. H. seriatus, ellipticus modice convexus, piceo-niger nitidus confertim 

 punctulatus, thorace latitudine duplo breviore, linea utrinque antica discoidali, 

 punctisque paucis ad latera notato, elytris striis punctatis, internis antice leviori- 

 bus, euturali antice bifida, alternatim punctis maioribus in strias impressis : tibiis 

 tarsisque ssepe rufo-piceis ; mesosterno lamina parva triangulari armato. Long. 

 28. 



California, at San Francisco and at the Colorado river. The large punctures 



