OF PHILADELPHIA. 185 



This species exhibits the general form of hrevicornis, but the 

 the thorax is proportionally much narrowed, and the characters 

 above detailed prove it to be very distinct from that species. 

 The lepaceous processes of the antennae are so profoundly emar- 

 ginate beneath as to appear each bilobate. I obtained it on the 

 Arkansa river near the Mountains. 



3. P. PALPARIS. — Black ; thorax tridentate ; terminal joint of 

 the maxillary palpi longer than the preceding one. [328] 



Inhabits the upper part of the Arkansa river. 



Body black, immaculate, punctured ; head confluently punc- 

 tured ; an impressed, longitudinal line : maxillary palpi with the 

 last joint longer than the penultimate one : thorax, punctures 

 rather more sparse on the disk ; lateral margin not dilated ; edge 

 tridentate ; anterior tooth a slight prominence of the anterior 

 angle ; intermediate one acute, subconic, spiniform, not reflected ; 

 posterior tooth not prominent, and consisting only of the poste- 

 rior angle : elytra slightly punctured, nearly smooth ; tip slightly 

 mucronate : pectus and postpectus of the male hairy ; hair yel- 

 lowish. 



Length, male one and one-fifth, female one and a half inches 

 nearly. 



I observed several specimens of this species on the Arkansa 

 near the Mountains. It resembles at first sight P. hrevicornis 

 Fab., but it differs from that insect in some important characters, 

 the elytra are much smoother, the thorax is not so broadly mar- 

 gined on each side, the intermediate thoracic tooth is more spini- 

 form ; but the most characteristic difference appears to reside in 

 the maxillary palpi the terminal joint of which is very conspicu- 

 ously longer than the preceding joint, whilst the corresponding 

 parts of imbricornis are nearly equal. 



4. P. CILIPES. — Castaneous; thorax minutely dentate; tibia 

 ciliate on the inferior edge. 



Inhabits Platte and Arkansa rivers. 



Body castaneous, punctured ; head thorax and [ 329 ] extrem- 

 ities blackish : head with a longitudinal, impressed line ; punc- 

 tures sparse between the eyes, more dense before, upon the man- 

 dibles, basal joint of the antennae, and becoming scabrous on the 

 1823.] 



