NEOTROPICAL PLATYRHACID MILLIPEDS — HOFFMAN 



23 



Antennae closely spaced (isthmus 1.5 mm. wide), rather long 

 (9.0 mm.) and robust, reaching back to middle of thnd paranotum; 

 articles clothed with long sparse setae; articles 2-5 subequal m size 

 and shape; 6 longer, without evident distal sensory areas; 7 small, 

 subconical, its distal margin inturned and separating the fom- sensory 

 cones. 



Collum rather small (7.1 mm. wide, 4.0 mm. long) and modified 

 as follows: Anterior third of surface and most of the short, acutely 

 triangular paranota nearly flat and smooth, without anterior marginal 

 row of tubercules and postmarginal transverse furrow; posterior 



Figure \.—a,b, Platyrhacus kerri (Cook) :fl, Mesial aspect of left gonopod of male holotype; 

 b, outline of left paranotum of 18th tergite; c, Platyrhacus acanthopleurus, new species, 

 mesial aspect of left gonopod of male holotype; d, Nyssodesmus atUnisi, new species, 

 mesial aspect of left gonopod of male holotype; f, Psammodesmus atratus (Chamberlin), 

 mesial aspect of left gonopod of male holotype. 



