NO. 1170. THE FAMILY GOMPHODESMIDJE— COOK. 723 



and robust body, the sliorter legs and antennte, the semicircular first 

 segment, and the large spines of the copulatory legs. 



The five species which are associated under the present name may 

 not prove to be a natural group, but if they do not belong together it 

 seems unlikely that they can be located under any of the i^receding 

 genera. 



A.VALYTICAI. KEY TO THE .SPECIES OK SIGODESMfS. 



Length, 47 mm, ; flagellatn ending in a thickened node-like expansion from which 

 projects a single curved prong: Sigodesmus monocerun, p. 724. 



Length, 40 mm., or under; flagellum ending in two distinct, slender, or at least 

 pointed, prongs 



Length, 40 mm.; flagellum ending in two strongly curved, connivent prongs, the 

 longer of which is strongly recurved near the apex and has a sharp tooth near its 

 base: SigodeHmuH riinpolU, \i. 72."). 



Length, less than 30 mm. : prongs not so strongly connivent, the longer not 

 recurved at apex, and without a tooth at base 



Flagellum without other processes than the terminal prongs, one of which is over 

 twice as long as the other: Sujodesmua indiguH, p. 723. 



Flagellum with a small lateral process below the base of the more robust of two 

 prongs, which are subetjual in length 



Lateral process mentioned above very small, acute, and spiniform: Sigodeamus 

 contortuK, p. 72.5. 



Lateral process subrectangular, nearly as wide as the flagellum opposite the 

 process: Sigode6niu*i innotatiis, p. 726. 



SIGODESMUS INDIGUS, new species. 

 (Plate LIX, figs. 2o-2c.; 



Vertex without hairs, strongly convex, suture and sulcus distinct. 



Clypeus with two minute setiferous punctations between the anten- 

 nal sockets, somewhat closer to each other than to the sockets; another 

 pair of similar punctations lower down and wider apart; supralabral 

 punctations few and indistinct. 



Antennjj' rather sparsely hirsute with short hairs, the sixth joint dis- 

 tinctly sliorter and slightly thicker than the fifth. 



First segment without a trace of an anterior corner, the anterior mar- 

 gin being carried around to the posterior corner almost in a semicircle; 

 the posterior corner is more distinctly angled than in any other member 

 of the family here described, and the great length of the .segment is also 

 peculiar; the marginal callus is narrower than in any of the genera 

 which have a lateral angle. 



Segments dorsally finely coriaceous, somewhat rugulose on the 

 carina-. 



Lateral carina; of moderate width, distinctly narrower than in Antro- 

 desmus; anterior margin much more distinct than the x>osterior; mar- 

 ginal callus narrowed in front and broadened opposite the pore, so that 

 the poriferous carina; are more rounded than the others; the carina; of 

 segments 17 to 19 are rather broad, much shorter and broader than in 

 AstroflesmuH petilus. 



