484 ONISCID/E. 



length of the two terminal appendag-es of the tail. Herr 

 Schnitzler has, indeed, proposed to form it into a separate 

 genus, Cylisticus, on account of the convexity of the 

 terminal segment of the tail, the rectangular lateral 

 termination of the segments of the body, and the curious 

 character (to which he has first directed our attention) 

 that each of the false feet, or branchial plates of the tail, 

 are marked with small white spots at the base; whereas 

 in the other species it is only in the first and second pairs 

 of those organs that this character is to be found. These 

 characters do not appear to us, however, to be of suffi- 

 cient importance to warrant the establishment of a new 

 genus for the P. lavis. 



Its colour is of a leaden grey, occasionally blotched 

 with yellow on the sides. It is sluggish in its habits, 

 and occurs commonly in stable-litter, and among grass at 

 the bottom of walls. 



It occurs in England and Ireland. Kent, and the 

 neighbourhood of London and Dublin, have been re- 

 corded as the localities. 



