NOTODELPHYS. 129 



caudal segments and the position of the lateral setge 

 upon their external margins, together with the 

 appearance of the external margin of the first joint of 

 the outer branch of the first foot. The marginal 

 spines of this branch, the setose armature of the 

 second antennse, and of the fifth pair of feet, &c, 

 afford other means of specific diagnosis ; but it seems 

 to me that the distinctions are, in some cases, at any 

 rate, much too trivial, and that in all probability a 

 more extended investigation would lead to the conclu- 

 sion that at best some of these forms deserve to be 

 classed only as varieties. In the case of the present 

 species the distinctions drawn between it, N. rufescens, 

 and N. elegans, do not appear to be of specific import- 

 ance. 



As regards Mr. Airman's description and figures of 

 Notodelphys ascidicola, it must, I fear, remain doubtful 

 to which species of the genus they were meant to 

 refer j it is, indeed, more than probable — from the 

 number of localities given in Mr. Airman's paper that 

 several species of Notodelphys were the subjects of 

 description, while some of the figures (14, 15, and 21) 

 undoubtedly refer to a quite distinct genus — Ascidicola, 

 Thorell. It seems best, therefore, to follow M. Thorell, 

 discarding altogether the specific name Ascidicola, 

 which, however, will stand as the designation of a 

 separate genus. 



