PROCEEDINGS OF THE NATIONAL, MUSEUM. vol.61, 



h.' Somites with a second sulcus in front of tlie ordinary one. 

 c' The posterior transverse sulcus complete dorsallj', at least on segments 

 in middle of body, 

 rf.' Anterior sulcus weak and often interrupted, the posterior weaker, 

 anal tergite not surpassing the valves, and not acutely produced ;; 



black with brown legs R. leptopus Pocock. 



d.^ The two transverse sulci complete and deep on nearly all the segments. 

 e.* Larger species near 140 mm. or more in length and 13 mm. or more 

 in diameter. 

 Scobina extending to posterior region of body. 



R. thomasianus Chamberlin.. 

 e.' Smaller species near 60 mm. and under in length, 



f.^ Anterior transverse sulcus arising on each side from the lateral 

 portion of the posterior sulcus considerably below the pore; 

 color black, with on each segment a median dorsal flavous spot 

 and a lateral flavous spot over each pore. 

 j7.^ Anal tergite surpassing the valves. (Dominica). 



R. leucostigma Pocock. 

 g.' Anal tergite clearly exceeded by the valves. 



R. martiniquensis Chamberlin. 



A' Anterior transverse sulcus arising on each side in front of and on 



a level with the pore; segments distinctly flavo- or ferrugino- 



cingulate. 



g.^ Caudal process considerably surpassing the valves ; the area of 



the segments behind the posterior sulcus flavous. 



R. monilicomis Porat. 

 g.^ Caudal process scarcely or not at all surpassing the valves. 

 h.^ Length up to 60 rwni. with width 5 nun. or more (somites 



forty-seven or forty-eight) R. juxtus Chamberlin. 



h." Length near 35 mm., and width near 3 mm. 

 t.' Segments narrowly ferrugino-cingulate along caudal bor- 

 ders; median plate of male gonoiX)ds with sides straight. 



R. consociatus Pocock. 

 i.' Segments not bordered with ferruginous; median plate 

 of gonopods with sides convex proxinially and conspicu- 

 ously incurved or concave distad of middle. 



R. tobagoensis Ch.iniberlin. 

 r.' The posterior transverse sulcus obsolete dorsally on all or most of the 

 segments. 

 (/.' Anal tergite acutely angled posteriorly. 



e.' Transverse swlcus conspicuous laterally ; color as in vwniliconiis. 



flavo-cingulate R. ang'uinus Pocock. 



e.* Transverse sulcus obsolete, or nearly so, on most segments ; upper 

 surface of segments dark, with a flavous spot on each side of the 

 middle line. 



/.' Segments forty-eight to fifty-two R. serpentinus Pocock. 



/." Segments forty to forty-three R. grammostictus Pocock 



(/.' Anal tergite not acutely produced, rounded. 



c? Posterior portion of segments flavo- or ferrugino-cingulate. 

 f? Anal tergite clearly surpassing the valves. 



R. mimeticus Chamberlin. 



