COLEOPTERA. 157 



tate ; punctures round, deeply impressed, interspaces as wide as or wider than 

 the punctures, nearly flat, finely granulated, moderately shining. Elytra at 

 base one-sixth wider than the prothorax ; sides very feebly divergent poste 

 riorly, one-third longer than the width at base, nearly straight; together 

 narrowly and strongly emarginate behind ; suture one-third longer than the 

 pronotum ; surface narrowly impressed along the suture, each elytron with 

 three longitudinally disposed undulations ; punctures rather small, round, 

 deeply impressed, evenly distributed, distant by slightly more than their 

 own widths, interspaces finely granulose, shining. Abdominal segments 

 decreasing rather slowly but uniformly in width, first as wide as the elytra ; 

 border of first four segments very strong, then much narrower; surface very 

 finely and evenly punctulate, shining; transverse carinae not cusped. Legs 

 rather short, piceous -black, tarsi much paler, the latter very robust ; first, 

 second, and third joints of the posterior uniformly decreasing in length, 

 fourth very strongly bilobed, fifth small. 



Male. — Posterior edges of the second, third, and fourth ventral segments 

 feebly emarginate in the middle fourth, emarginations very feeble and round, 

 contiguous surfaces cylindrically impressed, the fourth most strongly so ; fifth 

 segment transverse and entire at apex, surface not appreciably impressed : 

 sixth strongly sinuate at apex, sinus more acutely rounded than the apices, 

 about twice as wide as deep; seventh segment broadly and evenly rounded 

 behind, dorsal armor very strongly developed, projecting beyond the ventral 

 portions. 



Female. — Sixth segment very strongly and acutely, abruptly and narrowly 

 produced at apex ; seventh broadly, strongly, and angularly emarginate at 

 tip. Joints of antennal club more robust, increasing in length ; last joint of 

 paljn' longer, first and second paler. 



Length 4.3-4.8 mm. 



Lake Quesnel, British Columbia, 16. 



This species is extremely closely allied to the European A. plan- 

 taris (Erichs.), but differs from it in several characters which should 

 undoubtedly be considered specific ; among these are the following, 

 drawn from the females of the two forms respectively. 



In the former the club of the antennae is moderately robirst, and 

 not darker or scarcely perceptibly so; in the latter the club is ex- 

 tremely large and prominent, and abruptly much darker in color. 



In the former the seventh ventral segment is deeply emarginate 

 behind; in the latter it is narrower at tip, where it is transversely 

 truncate. 



The elytra in the former are relatively longer and narrower, and 

 have the surface more unevenly undulated. The pubescence of the 

 former is longer and more coarse than in the latter. 



Notwithstanding these differences, the two specimens compared 

 above have a most striking mutual resemblance. 



