June, I9I3-] ROBERTS: NoTES ON HaLIPLID^ OF AMERICA. Ill 



Mr. C. G. Thomson. All, with the exception of boreaUs, also have a 

 thoracic fold, or plica, as a distinctive character. 



While the species are all small and much alike in general appear- 

 ance they should not be hard to separate. Borealis may at once be 

 recognized by the lack of any plica on base of pronotum ; longulus 

 is the most elongate, noticeably so, narrow and highly polished and 

 the thoracic plica is distinctly longer than in any of the other spe- 

 cies; strigatiis is distinguished by the lack of any maculation, the 

 truly strigate elytra, caused by the deep, blackened, closely placed 

 punctures, with their compressed, almost parallel sides. 



Riificollis, hlanchardi and pallidus are proportionately stouter 

 than the others, and of these three blanchardi may be recognized by 

 the strong sinuation of the apices of the elytra and acute exterior 

 angle, which characters are fully as pronounced as in borealis; pal- 

 lidus by the lack of any black markings, even on the base of the 

 elytra, and the flat prosternal process; riificollis by its black macula- 

 tion, usually distinct, apices of elytra rounded, prosternal process 

 depressed, or channelled, lengthwise. In the hundreds of specimens 

 of riificollis examined I have never seen a specimen, even when the 

 usual maculation has almost completely disappeared, that did not 

 have at least a narrow black basal margin. If doubt exists after sep- 

 arating by these general characteristics a reference to the full de- 

 scriptions should at once dispel it. 



PELTODYTES Regimbart. 



It is with a strong feeling of rebellion in my heart that I adopt 

 the generic name Pcltodyfcs of Regimbart for that of the well-known 

 and long-established Cncmidotns of Erichson. However, Illiger hav- 

 ing undoubtedly made this name a synonym of the Haliplus of La- 

 treille it could not be used, under the accepted rules, and we lose one 

 more name long familiar to all students and collectors of aquatic 

 Coleoptera. 



Peltodytes callosus Leconte. 



In addition to characters mentioned by other writers I find that 

 in this species the mid-metasternum is deeply depressed between the 

 middle coxae so as to leave the margins at base decidedly tumid, 

 while behind the coxae they are fine, but quite distinct, and nearly 



