1855.] 371 



d a. 



9. P. d i f f u s u s, ovalis convexus nigro-piceus vel picens nitidus, confertim 

 subtiliter punctatus, capite antice tboracisque limbo pallidiore, elytris margine 

 indeterminate testaceo, postice fimbriato, seriebus punctorum 4 solitis notatis, 

 stria suturali antice abbreviata, palpis tibiis tarsisque piceo-te.staceis. Long. 

 17 -25. 



Nebraska and California : the body is a little narrower in front, and less convex 

 than in the preceding. The prosteruum is not at all carinate, and the keel of the 

 mesosternum is horizontal in its iufjrior outline, as in the other specieB < f this 

 division. The Californian specimens are smaller, a little broader posteriorly, and 

 a little more convex tban tbose from Nebraska, but I cannot observe any suf- 

 ficiently definite difference to cause them to be regarded as another species. In 

 pale specimens the head is blackish with anterior pale spots. 



10. P. p e r p 1 e x u s, longior ellipticus convexus, confertim subtiliter punctatus 

 piceus, vel nigro-piceus nitidus, capitis lateribus antice, thoracis et ehuorum 

 limbo laterali angusto rufescemibus, elytris seriebus punctorum 4 solitis, stria 

 suturali antice abbreviata ; palpis tibiis tarsisque saepe testaceis, vel piceis. 

 Long. -17 -20. 



New York, Illinois, Lake Superior, Nebraska. Very closely allied to the pre- 

 ceding but distinguished by the narrower and regularly elliptical form of body. In 

 one specimen the anterior spots of the head, and the whole margin of the thorax 

 are testaceous, the pale border of the elytra is fimbriated posteriorly : the abdomen 

 is yellowish, with the middle brownish, and the feet are almost entirelv yellowish. 

 Color, however, is so variable in this genus, that it cannot be taken as character- 

 istic, and recourse must be had to form and sculpture, which are sufficiently 

 distinct, in all the species herein noted, to render their recognition a matter of 

 very small difficulty. 



11. P. ochraceus, ellipticu3 convexus, confertim subtiliter punctatus, nigro- 

 piceus, piceus, vel supra testaceus, limbo oniui et capite antice pallidiore, elytris 

 postice dilute fimbriatis, seriebus solitis punctorum baud conspicuis, stria siuurali 

 antice abbreviata, pedibus aut fuscis aut testaceis. Long. -13. 



Melsheimer, Proc. Acad. Nat. 2, 101. (var. immat.) 



Middle and Southern Sates : resembles P. nebulosus, but the punctures of the 

 upper surface are more distinct, and the prosternum is not at all carinattd. 



d b. 



12. P. c i n c t u s, ovalis magis convexus, nigro-piceus vel piceu?, nitidus con- 

 fertim subtiliter punctatus, capite macula utnuque antica, thoracis elvt'O- umque 

 lateribus ferrugineo marginatis, his punctorum seriebus 4 solitis notatis, stria 

 suturali antice abbreviata ; palpis piceo-testaceis. Long. -26. 



Variat, corpore piceo-testaceo, capite supra et subtus obscuriore. 



Ilydrophilus cinctus Say, Long's Expedition, 2, 276. 



Philhydrw limbalis Meisbeimer, Proc. Acad. Nat. Sc. 2, 101. 



Middle and Southern Stttes and Nebraska: for a type I am indebted to Dr. 

 Melsheimer. Almost as convex, but not so broad as P. rotuodatus, and readily 

 kuown by the mesosternum being dilated into a large quadrilateral venic.il plate 

 in front of the middle coxae. 



In answer to some questions regarding the difference between P. cinctus and 

 limbialis Dr. Melsheimer writes as follows : " the latter is larger, more oval and 

 less convex than the first ; the colored margins are aLo broader and all ill- other 

 characters more distinct, but notwithstanding these differences, i now consider 

 them as different sexes." Say in his description does not mendon the sutural 

 stria, but I learn from Dr. Melsheimer that it is quite distinct. 



13. P. b i f i d u s, ellipticus modice convexus, nigro-piceus nitidus, co t'^rtim 

 subtiliter punctatus, elyiris striis 10 profundi* notatis, internis antice pbliteratis, 

 suturali versus scutellum bifida ; margine Bulco longitudinali densius punctata: 

 thoracis lateribus rufo-piceis, palpis tarsisque fenugineis. Long. -28. 



29 



