The genera and species of symphyla. 17 



irregular longitudinal stripes (PI. 5, fig. 3 k), the nature of 

 which is unknown to me; in all the other species of Scolo- 

 pendrella the terminal surface opposite to it shows several 

 transverse lineSj which on each side converge to the base 

 of the area, and each of these stripes consists of many 

 exceedingly small spines arranged in a line (PI. 6, fig. 4 g) ; 

 the area is also generally more or less adorned with longi- 

 tudinal stripes (PL 6, fig. 4 ?i). In all species of Symphyla 

 the cerci terminate in one or two set^. One is very short or 

 sometimes absent, and has been omitted in the descriptions; 

 the other varies from being rather short to exceedingly long. 



In Scolopendrella the length of the cerci in proportion to 

 the last pair of legs, their length in proportion to their depth 

 and sometimes also to their breadth, the density and length 

 of their clothing, and the length of the apical seta present 

 excellent specific characters ; in Scutigerella the density of 

 their setas and the length of the distal set^e are always impor- 

 tant, but the proportion between length and depth is some- 

 times less constant, presenting differences in small and large 

 specimens (see especially on page 30 on Scut, immacu- 

 lata). 



G. Tactile Hairs on the Last Segment. — The essential 

 structure of these organs has been described by eai^lier 

 authors. Here I shall only direct attention to the rather 

 different shape, etc., of the calicles mentioned below in the 

 diagnoses of the genera. The length of the tactile sette is 

 scarcely valuable as specific character. 



IV. On the MoRrHOLOGY of the MoUTH-rARTS. 



It may perhaps be allowed to insert a short chapter on this 

 matter, though it lies outside the scope of the present paper. 



I have examined specimens of Scutig. imniaculata 

 (Newp.) and Scolop. vulgaris, n. sp., two species very 

 distant from each other. 



The best results were obtained from preparations cleaned 



VOL. 47, tart 1 NEW SERIES. B 



