ATOPETHOLID MILLIPEDS — HOFFMAN AND ORCUTT 



163 



joined at a flexible joint as in Arinolus. The telopodite is short and 

 stout with a slender mesially projecting solenomerite, immediately 

 distad of which the joint is flared into a distinct hyaline cuplike struc- 

 ture obviously homologous to the much smaller distal expansion of 

 Arinolus, and for which the name calyx is suggested. No trace of a 

 semmal groove could be detected. 



The illustration of the posterior gonopod published by Loomis is 

 made from the anterior aspect and presumably from a low magnifi- 



FiGURE 12. — Scobinomus serratus Loomis, male paratype from Ensenada, Baja California: 

 a, anterior gonopods, cephalic aspect; b, right side of anterior gonopods, caudal aspect; 

 c, left posterior gonopod, caudal aspect. 



cation. Consequently, the solenomerite was not shown, and the 

 similarity to the gonopod of Tarascolus was scarcely apparent. 



Distribution: The two known localities for this species are on the 

 Pacific coast of Baja California, not far south of the international 

 boundary. It is a matter of some interest that this form, obviously a 

 close relative of Tarascolus of the southern part of the Mexican 

 Plateau, should occur in such a geographicaUy isolated region. Possi- 

 bly futm-e coUections in the mountains of Sonora and Sinaloa will 

 disclose the presence of additional related forms and thus bridge the 

 present gap. As it stands, this discontinuity is another small but valid 

 reason for retaining Scobinomus as a separate genus, as such a magni- 

 tude of geographic isolation in Sonoran miUipeds usuaUy carries 

 corresponding structural diversification. 



