ATOPETHOLID MILLIPEDS — HOFFMAN AND ORCUTT 133 



laterad or else distinctly distad. The base of the telopodite is set 

 oflF by a marginal rim which projects slightly out beyond the end of 

 the coxite toward the opposite side. 



The posterior gonopods tend to be quite simple, the coxite and 

 telopodite merging into a broad consolidated subtriangular region 

 with no remaining trace of a joint at the point of the union. No 

 traces of a seminal groove have been detected, and nothing that might 

 be considered a solenomerite. The end of the telopodite may be 

 simple and laminate or strongly recurved, and a large subterminal 

 branch is present in Watichelus. 



There is some doubt attending our disposition of genera in this 

 subfamily. The generic name Orthichelus has been proposed for 

 species which differ only slightly from typical Atopetholus, and we 

 have therefore united the two names largely on the basis of the 

 "quaUty level" of degree of differentiation. Final resolution of the 

 matter awaits the attention of someone able to collect material from 

 numerous locaUties in southern California. The poorly known genera 

 Tidolus and Hesperolus may prove to be referable to this subfamily 

 when their type species are finally rediscovered and studied. 



Genus Atopetholus Chamberlin 



Atopetholus Chamberlin, 1918, p. 168. 



Onychelus (not of Cook) Verhoeff, 1938, p. 274.— Chamberlin, 1949, p. 169 (in 



part) . 

 Orthichelus Chamberlin and Hoffman, 1950, p. 7 (type species: Onychelus phanus 

 Chamberlin). 



Type species: Atopetholus califomicus Chamberlin, by original 

 designation. 



Diagnosis: An atopetholid genus characterized by the occurrence 

 of large accessory projections on the telopodite of the anterior gono- 

 pods just behind and below the apex of the joint. The absence of a 

 subterminal projection on the caudal margin of the posterior gonopod 

 distinguishes the genus from the related Watichelus. The lateral ends 

 of the collum are nearly symmetrically acuminate, in contrast to their 

 being bent caudally in Watichelus. 



Discussion: The taxonomic history of the group of species assem- 

 bled under this generic name has been unnecessarily complicated 

 and confusing owing chiefly to the failure of both Cook and Chamber- 

 lin to document adequately the descriptions of some of their new 

 forms. The diflSculty began with the proposal of Onychelus ohustus 

 in 1904, when Cook briefly remarked that the posterior gonopods of 

 the species are "concealed, simple, slender, falcate." No illustrations 

 were given for the species, and its really diagnostic characters have 

 remained unknown for almost half a century. In 1923 Chamberlin 



