THE I'REDACEOUS DIVING BKKTLKS. 217 



r. 'I'horax strongly margined, sparsely but distinctly imnclatc. 



417. sTAHNALis. 



ee. Thorax finely margined, almost smooth. OHI.IH s. 



dil. Under surface reddish-brown; prosternal process small; head and 

 thorax darker than elytra. 418. VILIS. 



mi. Hind coxa? contiguous. 



/. Form elongate, obconic; antenna? of male with joints 3-5 dilated; 



length 5.5-G mm. 419. DIFFORMIS. 



//. Form oval or oblong-oval; antenna? of male not dilated; length not 



more than 5 mm. 

 //. Under surface reddish-brown ; side margins of thorax generally 



thickened. 



//. Elytra coarsely punctured, with two smooth, narrow lines on 

 each; above black or piceous. head and elytral markings dull 

 yellow. 420. STRIATOPUNCTATI'S. 



Itli. Elytra without smooth lines. 



/. Clypeus rounded, broadly margined; elytra blackish with bars 



or spots of reddish-brown. 



j. Thorax finely and indistinctly margined. 421. CONSIMILIS. 

 jj. Thorax broadly and distinctly margined. 422. INUULATTS. 

 //. Clypeus rounded, not margined. 



k. Elytra blackish with yellow markings; form elongate-oval; 

 thorax not iufuscate. MIXTUS. 



A7.'. Elytra reddish-yellow with elongate or oblong black mark- 

 ings. 



/. Thorax with base and apex fuscous ; form convex ; sur- 

 face with dense fine yellow pubescence. SERICEI s. 

 //. Thorax narrowly fuscous at base ; form subdepressed ; 

 pubescence much less distinct. 423. DIMIDIATUS. 

 (>(/. Under surface (except sometimes the abdomen) black or piceous; 



side margins of thorax not thickened. 

 m. Thorax evenly and regularly punctate. 



//.' Punctures of elytra distinct ; length 4 mm. 424. NIGER. 



mi. Punctures of elytra indistinct; length 5 mm. 425. MODESTUS. 



mm. Thorax unevenly and irregularly punctate, the disk often smooth. 



or nearly so. 



o. Thorax finely and somewhat indistinctly margined at the sides. 

 p. Abdomen reddish-brown, paler than meso- and metathorax ; 



elytra finely and indistinctly punctured. 



q. Elytra piceons; form more slender and parallel; length 

 3-3.5 rmn. 426. PROXIMI s. 



qq. Elytra reddish-brown ; form broader in front, more pointed 

 behind; length 4 mm. 427. DICHROI s. 



pp. Abdomen black or piceous, not paler than meso- and meta- 

 thorax ; elytra distinctly punctate; length 4 mm. 



428. AMERICANUS. 



oo. Thorax distinctly margined at sides ; black, legs reddish-brown ; 

 length 4 mm. TENEBROSUS. 



