688 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxi. 



Process of sternum of sixth segment semicircular, triangular, subquadrate, and 

 medianly distinctly ajiiculate, or slender ; Hagelluni slender from the base or at least 

 with a long, slender, strongly curved or llexuous distal prolongation 



Copulatory legs enormously elongate, much larger than the unmodified legs; the 

 flagella strongly decurved, then turned laterad and expanded, slender and attenuate 

 distad, the apex lying under the carina of segment 6: Genus Neodesmus, p. 694. 



Copulatory legs mostly shorter than the others, turned mesad so that the flagella 

 cross each other, or at least are not projected laterad; not expanded in the middle, 

 the apices of the flagella lying near the median line 



Sternum of segment 16 of male with a small, distinct, subconic process located at 

 the middle of the anterior edge of the posterior subsegment; process of segment 6 

 twice as long as broad, somewhat narrowed in the middle, the distal corners promi- 

 nent, the apical edge distinctly bidentate: Genus Tycodesmus, p. 697. 



Sternum of segment 16 unmodified ; process of segment 6 as broad as long, distally 

 simply apiculate 



Lateral carinje, especially the anterior, not sloping in the direction of the dorsal 

 arch, but nearly horizontal; anterior segments with their posterior corners thick- 

 ened, the very broad marginal calli there not clearly defined mesad: Genus Omo- 

 desmus, p. 700. 



Lateral carina^ sloping nearly in the direction of the dorsal arch ; anterior carime 

 not thickened ; their marginal calli not broader, clearly defined 



Preanal scale with setiferous tubercles greatly enlarged, papilliform, much exceed- 

 ing the apex; first segment with anterior and posterior margins converging to a 

 somewhat symmetrical and produced, rounded lateral corner, the apex of which is 

 occupied by the widened marginal callus ; sterna of males without transverse ridges ; 

 sternum of segment 15 without a process: Genus (ioiiiphodesmiis, p. 704. 



Preanal scale with setiferous tubercles scarcely exceeding the apex; first segment 

 with lateral corner not produced, the Ciillus not widened; segment 15 with a sub- 

 triangular process from the anterior edge of the sternum ; sterna of other large forms 

 with a distinct, transverse, medianly interrupted ridge between the bases of each 

 l>air of legs .> 



Flagella of copulatory legs extended cephalad and downward in a simple and 

 regular curve, so that their apices lie near their bases and are directed downward 

 and backward; utodus with a large and broadly mammillate lateral prominence; 

 first segment much narrowed laterad: Genus Tymbodesmuti, p. 707. 



Flagella with nearly two turns in a diffuse spiral, their apices lying between the 

 bases of the copulatory legs, directed dorsad and cephalad; lateral prominence of 

 nodus small and spiniform; first segment with a longer lateral side: Genus Aitlod- 

 esmus, p. 713. 



Series II. A STRODE SMI. Olfactory Cones 10. 



Female with the coxiu of the second pair of legs produced ventrad into cylindrical 

 processes which exceed in length the second joints of the legs aiid are densely hir- 

 sute with very long hairs: Genus Merodesmtts, p. 717. 



Females of Astrodesmus, the only genus comparable in size and habit, with coxae 

 not produced 



Sternum of segment 15 of male without a process ; sternum of segment 6 with a semi- 

 circular, minutely apiculate jjrocess; flagella of copulatory legs accommodated by 

 a depression in the anterior part of the ventral surface of the seventh segment; first 

 segment with lateral side evenly rounded, its raised margin scarcely thickened: 

 Genus Splienodesmus, p. 719. 



Sternum of segment 15 of male with a subtriangular process; sternum of segment 

 6 with process triangular or subquadrate and apiculate; flagella of copulatory legs 



