134 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iii 



described under the name Onychelus nigrescens an atopetholid from 

 Coronado Island, Gulf of California, in which the gonopod was much 

 like that described by Cook. His example was followed by VerhoeflP 

 (1938) in naming 0. michelbacheri from southern California, and finally 

 Chamberlin added another related species, 0. phanus, from the same 

 general area. 



The history of Atopetholus developed simultaneously with but 

 independently of that of Onychelus. Proposed in 1918, Atopetholus 

 included species in which the posterior gonopod is slender and falcate, 

 with a recurved tip, and in which the telopodite of the anterior gono- 

 pod is provided with an accessory process. Apparently Verhoeff was 

 unaware of this paper for his knowledge of the name Atopetholidae 

 seemed limited to its use as a heading in Chamberlin's 1923 contribu- 

 tion. He thereupon rejected it as a nomen nudum and proposed the 

 new name Onychelidae, a name unfortunately based upon a milliped 

 not even in the same subfamily with the true Onychelus of Cook. His 

 species Onychelus michelbacheri, indifferently described and illustrated, 

 appears to be a fairly typical form of Atopetholus in the sense here 

 adopted. 



Onychelus continued to be used for quite a variety of millipeds until 

 1949, when Chamberlin restricted it to obustus, michelbacheri, phanus, 

 and nigrescens and proposed the new names Oosichelus and Watichelus 

 for species that had been previously described as forms of Onychelus. 

 At the same time, however, the long-lost type material of 0. obustus 

 was found among Cook's effects and returned to the U.S. National 

 Museum. An examination of the gonopods showed at once that 

 Cook's description was quite inaccurate, as the posterior elements are 

 actually arcuate and distally bifid and both these and the anterior 

 gonopods are totally different from those of the other three species 

 mentioned above. Actually, two other millipeds had been described 

 that are very close to obustus, although Chamberlin (misled by Cook's 

 description) placed them in the new genus Gosichelus. This discovery 

 led to the subsequent relegation of Gosichelus to the synonymy of 

 Onychelus and the proposal (Chamberlin and Hoffman, 1950) of the 

 new generic name Orthichelus to include phanus, michelbacheri, and 

 nigrescens. 



The question that we have had to consider is whether the variation 

 in the posterior gonopod justifies retention of Orthichelus as a valid 

 genus. Upon weighing all of the available information, we cannot 

 find any support for this course. Whether or not the extreme tip of 

 the gonopod is recurved to form a terminal hook appears to be a very 

 weak basis for a generic name, particularly when all other characters 

 appear to be the same in typical species of Atopetholus and Orthichelus. 

 There seems to be some variation in the development of the terminal 



