THE GENERA AND SPECIES OF SYMPHYLA. 23 



VI. Descript(on op the Cteneka and Species. 



The group consists of one single family with two genera.^ 

 In order to facilitate a comparison of the diagnoses of the 

 genera both are placed here. 



Gen. 1. Scutigerella, Ryder, 1882. 

 ('Proc. Un. States Nat. Mus./ vol. v, 1882, p. 234.) 



The posterior margin of thirteen dorsal scuta 

 (all scuta with exception of the last one) is either 

 slightly convex or e mar gin ate, the lobes on each 

 side of the middle of the emargi nation often 

 broadly rounded, rarely angular, and in this case 

 several times broader than long. 



The head is posteriorly at the middle sharply 

 defined from the neck; the two short rods con- 

 verging to the posterior end of the central rod 

 are at most moderately developed. 



The anterior surface of the posterior pair of 

 legs with a considerable or large number of setse. 



The cerci without stripes on the terminal area, 

 and without transverse lines on the most distal 

 part outside that area. 



The sense -c allele s near the base of the cerci very 

 irregular, the anterior and lateral parts of its 

 wall being vertical and the posterior part very 

 oblique; a large portion of the margin of the 



1 Some zoologist will perhaps soon establish these genera as families, and 

 divide each of them into two or more genera. In our present state of know- 

 ledge I disapprove such proceeding. Many authors are, in my opinion, too 

 liable to subdivide into families and genera, with the result that it is often 

 later on, when many new forms have been discovered, found necessary to 

 establish new and often badly defined genera, etc., in order to bring about 

 equivalence ; and it is more easy to establish bad genera than to get them 

 cancelled definitely again. 



