192 REVISTA CHILENA DB HISTORIA NATURAL 



of valué. Dorsal chaetotaxy:(16>^^, ^, ^, ^ , 



4 2 4—2 4 2 T^ 4 2 4 2 



TT' 18-' 18"' ^'^^'^^ chaetotaxy: 21, 12, -^, -^, 



4—3 4—5 4—2 4—2 4—2 

 ~2r' "24"' ~22~' 18^' "ÍS"" 



The chaetotoxal formulas are essentially as described 

 above for Chthonius, with the foUowing differences. In 

 the dorsal chaetotaxy the first figure (in parenthesis) re- 

 presents the number of setae on the posterior border of 

 the carapace. The chaetotaxy of the tergites aud sterui- 

 tes (except the first sternal segment) are represented frac- 

 tionally. The numerator refers to all setae except those 

 found along the posterior border, which are represented 

 by the denominator. The first figure in the numerator refers 

 to the setae found at the distal end of the tergite or ster- 

 nite in question, while the second figure median refers to 

 the number of setae found adjacent to the longitudinal 

 división. 



In this group, since all tergites and sternites are di- 

 vided by this longitudinal suture, all figures raust be di- 

 vided by two to give the chaetotaxy of each tergal or 

 sternal half. The first figure in the ventral formula refers 

 to the number of setae found along the posterior border 

 of the genital operculum. 



