ATOPETHOLID MILLIPEDS — HOFFMAN AND ORCUTT 157 



Surface of collum smooth and polished with a few fine punctations; 

 the lateral ends not produced caudoventrad and not extending below 

 the level of second segment. Pleural lobe of second segment with a 

 low but distinct anterior marginal run. Pleurotergites generally 

 smooth but with small scattered punctations, otherwise similar to 

 those of torynophor. 



Anal segment smooth with tiny punctations; anal valves with 

 several small transverse grooves and striae. 



Sternites more nearly rectangular than in torynophor, only slightly 

 wider in front than behind. 



Sympleurite of seventh segment (figure U,d) strongly produced, with 

 a distinct median notch and longitudinal depression. 



Anterior gonopods (figure ll,a,6) with the sternite distmctly arched; 

 shape of the coxites obsciu-ed by the heavily folded intersegmental 

 membrane, which is produced mesially into a sort of "pseudosternite." 

 Coxites impressed near the lateral margin by a deep vertical groove, 

 giving the impression of distinct accessory lateral pieces. Apices of 

 coxites strongly produced distad, and slightly curved laterally, the 

 tips rounded. Telopodites visible in anterior aspect, their apices 

 likewise drawn out and directed laterally, only slightly exceedmg the 

 level of the coxal projections. Posterior gonopods rather small and 

 short, the telopodite in particular much less enlarged distally than 

 normal for the genus (figure 11, c). 



Discussion: Variation: The segment number in three males is 40, 

 41 , and 42 ; in the female, 44. Clypeal foveolae range from 3-3 to 4-4. 

 The ocelli in two males are 26-27 and 27-28; in the female, 37-39. 

 There is some reason to suspect, therefore, that either the female 

 belongs to a different species (despite having identical external char- 

 acters), or that sexual dimorphism is more pronounced in this group 

 than in the Eurelinae. This latter alternative is probably the correct 

 one, as sexual differences are usually more pronounced m more special- 

 ized or evolutionarily advanced forms. 



Distribution: Known only from the type locality, and possibly 

 endemic to the Santa Catalina Mountains. 



Arinolus hopinus Chamberlin 



Arinolus hopinus Chamberlin, 1941a, p. 12, fig. 16 (male holotype in the Cham- 

 berlin collection, from 16 miles east of Tucson, Pima County, Arizona, 

 collected on December 28, 1941, by Stanley and Dorothea Mulaik). 



This name was placed by Loomis in the synonymy of A. hospes 

 (Cook), a disposition that may be entu-ely correct. Yet until the 

 Tucson region has been so thoroughly studied that it is certam only 

 one Arinolus occurs there, we thmk it safer to avoid premature 

 rejection of Chamberlin's name. 



