MILLIPEDS OF MEXICO AND CENTRAL AMERICA 77 



equalling or surpassing tips of anterior plates (coxae or coxal 

 endites), which usually are mesally produced; distal joint of inner 

 gonopods elongate, usually quite slender and outwardly bira- 



mous RHINOCRICIDAE 



Prozonites without scobinae; anterior sternal plate of gonopods 

 transverse, subtriangular, or rarely distally produced; inner gono- 

 pods usually short and stout, not biramous near apex 2 



2. Inner gonopods with apical and basal elements forming a continuous 



inward curve SPIROBOLIDAE 



Inner gonopods with apical and basal elements not forming a continuous 

 inward curve 3 



3. Inner gonopods with outer joint in a nearly continuous straight line, 



with basal elements heavy ALLOPOCOC KIIDAE 



Inner gonopods with each terminal joint at an angle to the coxal 

 element; lowest joint slender 4 



4. Anterior gonopods with mesal margins long and in contact much of 



length; segment 2 usually with a spirobolus-like production below 



lateral angle of segment 1 MESSICOBOLIDAE 



Anterior gonopods with mesal margins short or, if elongate, gen- 

 erally well separated, rarely in contact for a short distance; seg- 

 ment 2 seldom much produced below lateral angle of segment 1 . . 5 



5. First segment with front and back margins each side converging 



downward to an acute angle ATOPETHOLID AE 



First segment with front and back margins each side not strongly 

 converging downward; lateral margin broadly rounded. 



SPIROBOLELLIDAE 



Family ALLOPOCOCKIIDAE 



In his treatment of this family in 1960, Keeton did not mention the 

 genus Arolus Chamberlin 1922 although it was described as closely 

 related to Allopocochicu He also appears to have overlooked the paper by 

 Kraus 1954 in which Arolus was placed as a synonym of that genus. 

 He did consider \\\atChelogonoholus mightbe a synonym oi Allopocochia 

 but lack of material for study caused him to withhold judgement. It 

 appears to me that Arolus purulanus offers distinct connection of these 

 two genera but they are still kept apart until further study of Allopocochia 

 tylopus can be made. 



Genus ALLOPOCOCHIA Brolemann 1913, p. 478. 



Arolus Chamberlin 1922, p. 34; Kraus 1954, p. 336. 

 TYPE SPECIES: Spirobolellus tylopus Pocock, by original designa- 

 tion. 



