A Preliminary Bevision of the Genus Trisuloides 409 



It will be noticed that one species included by Hampson in 

 Trisuloides is omitted from the foregoing scheme of the genera : the 

 Palaearctic Acronicta cornelia Stgr. This is only known to me from 

 a single specimen in coll. British Museum, and I have had no 

 opportunity of diagnosing it according to the system employed above. 

 It appears to me, however, so far removed from all other Trisuloides 

 species that there is little doubt that Warren is correct in erecting 

 for it a separate genus; in which case it will stand as Xanthomantis 

 Warr., Seitz' " Macrolep.," iii, p. 18 (1909). 



Acronicta cornelia Stgr. (type). 



MODIFICATIONS OF GENITALIA. 



The species examined in the group of genera dealt with here exhibit 

 a certain similarity of structure, and one may trace the development 

 of certain organs. 



All the species agree in the valve possessing a fold along the dorsal 

 and ventral edges. The ventral fold has become modified to form 

 a chitinous process. This is seen in its most simple form in Anepholcia 

 pygaria, in which a portion of the fold is free from the other mem- 

 branous part of the valve. In A. talboti this is carried a step further, 

 the free end of the fold being shortened and less curved, whilst an 

 attempt to develop a second process is seen on the dorsal fold. The 

 development of two processes is seen in Disepholcia caerulea, and it is 

 possible that some forms may still be found in which the development 

 of two processes is less pronounced. 



The development of the process from a finger-like smooth appendage 

 through an increasing chitinization to a strongly chitinized and toothed 

 appendage is seen in A. pygaria, talboti, D. caerulea, T. variegata, 

 glauca, the Anacronicta forms, Smilepholcia, and finally in Trisuloides. 



Similarly with the uncus, we may trace modifications from the short 

 and broad type to a sickle-shaped and narrow type, the ormer repre- 

 sented by D. caerulea, thence through Trisuloides, Anepholcia, Smile- 

 pholcia, to Anacronicta. 



The presence or absence of cornuti on the eversible membrane of the 

 penis is a character which, although not generically constant, is of 

 specific value. 



