98 ACADEM? OF NATURAL SCIENCES 



a longitudinal and oblique dilated line united in the form of a 

 W ; labium wliitc : thorax with a green disk and longitudinal 

 impressed line : elytra with punctured striae, green ; margin, two 

 undulated bands and tip, pale rufous; pectus and postpectus 

 darker rufous : feet whitish. 



Length more than one-fourth of an inch. 



I observed this species in plenty on Elk-horn Creek. The 

 elytra have a tessellated appearance in consequence of the un- 

 dulations of the bands being subquadrate, particularly the two 

 nearest to the disk. 



[Afterwards described by Dejean as 0. Lecontei. — Lec] 



COLYMBETES Clairv. 



C. VENUSTUS. — Reddish-yellow ; thorax at tip and base black ; 

 elytra dusky olivaceous with a pale external margin, interrupted 

 base and abbreviated subsutural line. 



Body reddish-yellow : vertex dusky : thorax, anterior [153] 

 margin to the eyes on each side, and posterior margin as far as 

 the middle of the base of each elytron, black : elytra dusky oli- 

 vaceous or blackish ; a yellowish exterior margin attenuated to- 

 wards the humerus, and a whitish external submargin composed 

 of three somewhat oblique approximate lines, of which the inner 

 one is abbreviated before the middle ; a dilated, subtriangular 

 white line from the humerus to the middle of the base, where it 

 abruptly terminates ; a subsutural white line from near the base 

 is attenuated and terminated before the middle ; disk with two 

 obsolete interrupted lines : venter each side dusky. 



Length one-third of an inch. 



Found many specimens in a pond near Bowyer Creek, Mis- 

 souri. It is also an inhabitant of the Atlantic States. I think 

 it probable that this is the Dytiscus interrogatus of Fabricius. 



[This was afterwards made the type of Copdotonms Say ; it dooh 

 not appear to diflFer from D. interrogatus. — Lec] 



HYDROPORUS Clairv. 

 H. PARALLELUS. — Black; elytra lincate with yellowish. 

 Inhabits Missouri. 



Body black : head before and a small obsolete spot on the ver- 

 tex, rufous : antenae pale at base, dusky at tip : palpi pale, tip 



[Vol. III. 



