70 Memoirs on the Coleoptera 



prothorax is said to be slightly narrowed posteriorly and very 

 feebly cordiform; in marginellus it is decidedly cordate and much 

 narrowed posteriorly. In bicolor the pronotum is covered with 

 more or less distinct undulated transverse rugulae, the anterior 

 impression strong and the posterior less deep though apparently 

 visible, the obscure brown elytra are slightly bronzed and with 

 smooth striae, and the under surface is obscurely green-bronze in 

 lustre, most of which characters differ sensibly from those of 

 marginellus, as can be seen from the above description. Bicolor 

 inhabits Kamschatka and, under the name riparius Gebl., is said 

 to occur also in Siberia. Marginellus resembles anchomenoides 

 somewhat, but the prothorax is much more narrowed basally, the 

 foveae not deeply linear as in that species but broadly concave, and 

 the elytra are much more depressed. Marginellus Er., (1842), 

 from Australia, probably belongs to another genus. 



Section Deratanchus. 



This section is limited at present to a single very isolated species, 

 described by G. H. Horn under the name Platynus quadrimaculatus, 

 with a query as to the genus. It was the opinion of the author 

 that a separate genus might have to be erected for it eventually, 

 but, as it comes very close to the decorus types of the preceding 

 section, in nearly all of its structural characters, I feel that a fully 

 distinct genus is not necessary under present lights; it however 

 differs greatly from any other North American species of the entire 

 subfamily, in its sharply bicolored maculation of the elytra. It 

 may be described as follows : 



Form elongate, moderately convex, dull throughout in lustre, testaceous, 

 the head black, the elytra black, each with a large testaceous basal 

 area and another posterior and discal, of testaceous color, the two 

 basal areas uniting at the base of the suture; epipleura black, pale 

 basally; under surface and legs pale testaceous, the abdomen black, 

 with a paler discal posterior area; head elongate, rhomboidal, three- 

 fourths as wide as the prothorax, the eyes moderate, midway 

 between base and apex, somewhat prominent; occiput with some 

 fine scattered punctures; anterior impressions fine, oblique; palpi 

 pale, with the fourth joint distinctly longer than the third; antennae 

 slender, more than half as long as the body, fusco-testaceous, the 

 four basal joints paler, the third much shorter than the fourth; 

 mentum tooth triangular; prothorax narrow, elongate, with the 

 sides very finely and equally reflexed throughout, broadly rounded, 



