246 A llonograjyh of Scytonotus. 



however, in comparison with other Polydesmid;e, that the high 

 degree of specialization of Scytonotus becomes apparent. 



To have the legs of males larger and stronger than those of 

 females is a character general, if not universal, in Polydesmidse. 

 There are, too, among the difierent genera different contrivances 

 to assist in copulation, for example, in Fontaria the claw of the 

 male leg is proportionally much larger and longer than in the 

 female, and stronglj^ decurved (figs. 44-45), while in Oxydesmus 

 (figs. 42-43) the claw is decidedly shorter in the males. 



Some of the special structures, such as the tuberculation of the 

 distal joint of the legs of males, Scytonotus has in common with 

 Polydesmus and Paradesmus,^ but in none of the genera is there 

 known to occur any such abrupt and apparently abnormal modi- 

 fications of shape and structure as are exhibited by the legs of the 

 13th-20th pairs, much less an}^ corresponding adaptation of the 

 female as the atrophy of the carinti? ; in fact, no similar case 

 seems to have been noted among the Diplopoda. 



Huntington, N. Y., 15 August, 1893. 



1 In Polydesmus the tubercles are more knob-like than in Scytonotus, 

 they appear on the three distal joints of the legs, and are seta-tipped, as 

 in Scytonotus. In Paradesmus the tubercles are to be found on four 

 joints, are conic, and without setae. 



EXPLANATION OF THE PLATES. 



PLATE VI. 



Scytonotus graiixilatus. 



Fio-s, 1-21. — Legs of the male, the number of the figures correspond- 

 ing to that of pair. 



Fig. 8. — Genitalium of male, median face. 



Fig. 13a.— The 13th leg, joints 3-5, posterior face. 



Fig. 13b. — The same, with joint 6, dorsal face. 



