410 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 117 



apical two abdominal sternites minutely and sparsely punctate. 

 Male genitalia mth ventral portions of lateral lobes continued back- 

 ward as two short spines; dorsal portions fused, forming a broad arc 

 posteriorly, but -with visible remnants of a much narrower fusion 

 (pi. 4, fig. 31). No apparent external sexual dimorphism. Meas- 

 urements: length 5.0-7.9 mm.; %vidth 2.7-4.2 mm. 



Remarks. — This species, the largest in northeastern North America, 

 is closely related to both P. incilahrum and P. laevipes. This con- 

 clusion is supported by a study of the male genitalia in which the 

 ventral portions of the lateral lobes are continued backward as two 

 spines and the dorsal portions are fused much farther posteriorly, 

 forming an arcuate bridge which more or less obscures their paired 

 nature (pi. 4, fig. 31). 



The larger size of P. subcostatum, its broader form, uniform dark 

 coloration without bluish or greenish reflections, the raised inner 

 margins of the eyes, and the lack of coarse longitudinal ridges on the 

 underside of the pronotum, should readily distinguish the majority 

 of specimens from P. picilabrum.. An excellent character is to be 

 found in the dorsal portions of the lateral lobes of the male genitalia. 

 In P. picilabrum these lobes are completely fused, forming a strong, 

 nearly straight bridge, while in P. subcostcdum, the traces of former 

 lines of fusion are quite apparent. 



P. subcostatum may be distinguished from P. laevipes by the shining 

 lustre of the dorsum, the consistently deflexed apex of the prosternal 

 process, the flatter, more strongly punctured elytral intervals, the 

 more feebly impressed and more finely punctured elytral striae, and the 

 very narrowly margined pronotmn. There are no clearcut differences 

 in the male genitalia. In P. subcostatum, the acute dorsal groove of 

 the basal sclerite and the struts in repose protruding substantially 

 beyond the base of the sclerite appear to be constant and diagnostic 

 characters. In addition, the relatively larger size of the entire 

 aedeagus is a useful criterion. 



Type. — Not seen; type locality listed as Philadelphia. The type 

 of P. clypeatum Haldeman (MCZ 8368) is a typical specimen of P. 

 subcostatum and was placed under that name by LeConte in his 

 collection. It bears a "Middle States" label. Ohio specimens cor- 

 respond to the types of P. oblongulum in UMMZ (Kelejnikova, in 

 litt.). Type locality, "Florida." 



Specimens examined. — From the following localities, 763 : 



United States: Alabama (Barton, Selma, Tuscaloosa). Arkansas (Hot 

 Springs). Connecticut (Cornwall, Hamden, New Haven). Delaware (Bombay- 

 Hook, Glasgow, Newark, Seaford). District of Columbia. Florida (Brooks- 

 ville, Cresent City, Enterprise, Suwannee River). Georgia (Athens, Atlanta, 

 Clayton, Cornelia, Dunwoody, Savannah, Tybee Island). Illinois (Forest 



