No. 1810. DESCRIPTIONS OF NEW MILLIPEDS—COOK. 157 



Four specimens were examined, a male being selected as type. 

 All four were in a broken condition, so that the proportions of the 

 body and the numbers of segments could not be stated with certainty, 

 though the matching of the pieces allowed the same number of seg- 

 ments to be counted in all four cases. 



This species is evidently very distinct from Spirobolus nietanus 

 Saussure, which Pocock has recently transferred to his genus 

 Cyclothyrophorus. 



Genus ONYCHELUS Cook. 



Onychelus Cook, Myriapoda of Northwestern America, Harriman Expedition, 

 p. 67. 



The type of this genus, 0. obustus, was from the Colorado desert of 

 California. Specimens now in the National Museum seem to repre- 

 sent three additional species of Onychelus from the deserts of Arizona. 

 When the original description was drawn Onychelus appeared to have 

 no close relatives in the North American fauna. Several points of 

 difference between Onychelus and its undiscovered relatives were not 

 anticipated in the original description. Several additional peculiari- 

 ties of Onychelus have been noted in comparing it with Eurelus, as 

 the description of that genus will show. 



ONYCHELUS HOSPES, new species. 



Type. — Cat. No. 803, U. S. National Museum, collected at Tucson, 

 Arizona, December 23, 1896, by H. G. Hubbard, in the nest of a rat 

 (Neotoma albigula). 



Diagnosis. — Distinct from Onychelus obustus in the smaller size of 

 the body and in the position of the transverse constriction of the 

 segments. 



Description. — Body about 25 mm. long by 2.5 mm. in diameter, 

 probably composed of 4 1 or 42 segments. All the specimens are broken 

 and may not be fully mature. 



Color nearly black, with pale posterior margins. 



Clypeal foveolre four on each side. 



Eyes composed of about 33 ocelli arranged in an oval cluster of 

 seven rows: 3, 6, 6, 6, 5, 4, 3. 



First segment with two or three very short rudimentary striations 

 above the lateral angle. The segment is somewhat less strongly 

 emarginate in front and with a somewhat broader and less promi- 

 nent raised margin. The posterior margin is not so straight as in 

 0. obustus, but is distinctly curved forward above the angle. 



Segments very minutely punctate-striate, much more distinctly 

 than in 0. obustus. The stria? of the forebelt and ventral surfaces are 

 slight and indistinct, much as in 0. obustus. The transverse con- 

 striction is in the midbelt of the segment, instead of following the 

 posterior suture as in 0. obustus. This brings the repugnatorial pores 



