680 PROCEEDINGS OF THE NATIONAL MUSEUM. volxxi. 



located between the bases of the sixth pair of legs: Harmodesmus, 



MarptodesmuH. 



4. Sterimiii of sixth segment with a similarly located very broad, thin 

 aud lamcdlar i)rocesis divi<led nearly to base into two semicircular lobes: 

 UlodeHmun. 



5. The ])rocess broader than long, subquadrate, distinctly and broadly 

 excised distally: MychodcKinus. 



(). The process slender, qnadritubercnlate distad: Tycodesmus. 



7. The i)rocess is senucircular, sub<piadrate, or triangular, about as 

 broad as long, medianly more or less apiculate: Astrodesnms and all 

 genera not mentioned under the four preceding nnnd)ers. 



S. The posterior edge of the rim of the aperture in which the copula- 

 tary legs are inserted is deeply and broadly emarginate, leaving a pair 

 of prominent laminate processes at the bases of the normal legs of the 

 seventh segment: 2)jcodcsmiis, Tymhodcsmus. 



9. Transverse ridges between the posterior pair of legs of segment 8 

 short (narrow) and much more prominent tlum the others: Tycodcfimns, 

 I'ynthodcuiuus, Omodesniiis, and in a less degree, Astrodesmns. 



10. SternniM of segment 15 with a median subtriangnlar, distally 

 rounded, medianly canaliculate i)rocess directed (',ei)halad and ventrad: 

 A.strodesmiis and all the larger genera excejit (tomphodcsmns and Tyro- 

 dcsmus: the smallest gen(U'a, (n<>d<'smn.s, Alychodefinius, Neodesnms, and 

 ISplicnodesmns, are Avithont such a ])rocess. 



11. Segment 1(5 with a small papilliform process located similarly to 

 the ])rocess of segment IT) previously described: Tycodcsmiis. 



12. Second male legs with (;oxa^ ])rodii(;e(l (ventrad), most in Ohio- 

 desnins. 



13. First pairs of legs of male ])rovided with a tleshy sole at the 

 apex of the last. joint; present in all known specimens. 



14. The claw is more or less distinctly reduced, being most reduced 

 in genera with crassate legs and large soles. 



15. Anterior male legs with joints I to <> more or less tubeiculate on 

 the ventral face: Astrodastnusj Marptodcsmiis, ;\nd ])robably most of 

 the other genera. 



1(). Anterior male legs with second Joint strongly inllated on the 

 dorsal side; this feature appears in aU the genera as far as known. 



17. In the genus Merodannus the coxa^ of the second legs are greatly 

 produced ventrad and beset with very long hairs. 



IS. In Gomphodesnins the coxse of the second legs are somewhat i)ro- 

 dnced and on the lateral side areexi)ande(l and bear two rounded, tlat- 

 teued processes. 



19. In Gomidiodefimns the ventral part of the third segment of the 

 female is prodnced into a tliin ])rominent rim, which is deeply and 

 broadly emarginate in the middle to accommodate the second pair of 

 legs. 



The copulatory legs of the Gomphodesmidie are constructed on a 



