4 Mr. E. Meyrick on the 



found a rapid degradation, causing the obsolescence of 

 most of the veins, so. that the affinity of these forms, if 

 they stood alone, could not possibly be demonstrated. 

 The progressive obsolescence of the veins takes place as 

 follows, all the stages occurring in different genera : the 

 fission of the wings, occurring opposite the middle of the 

 cell, causes 5 and 6 in both wings to become very short, 

 but these veins, with the transverse vein, though 

 becoming very indistinct and feeble, do not disappear, 

 except in the extreme type Cosmoelostis, where the fissure 

 extends more than two-thirds of the length of the wing ; 

 in the fore wings 2 and 3 then become gradually coincident 

 with 4, and 7, 9, 10 and 11 with 8 ; in the hind wings 3 

 becomes coincident with 4, and in the extreme type 2 

 also coincides with 4 and 8 with 7. The neuration is 

 thus finally reduced to four simple independent veins in 

 the fore wings, and three in the hind wings. Keeping in 

 mind the principles that a vein once merged by coin- 

 cidence cannot possibly reappear, and that a fissure once 

 made can never be filled up, there is no difficulty in 

 constructing a genealogical sequence of the genera, 

 which will show, if not certainly the actual, at least a 

 possible order of development. The genealogical con- 

 nection is indicated, as far as possible, in the generic 

 descriptions hereafter following. 



Regarding the connection of the Pteroplioridce with 

 the other families of the Pyralidina, it may be pointed 

 out that the development of the uncus shows that they 

 are not derived from the Botydidce, and the separation 

 of vein 7 of the fore wings that they are not derived from 

 the Pyndid'uUe, whilst the absence of any pectination of 

 the lower median vein of the hind wings indicates that 

 there is probably no immediate connection with the 

 Cramhidce or Phycididce. From the other families they 

 mostly differ by vein 8 of the hind wings not anastomo- 

 sing with 7, and it is therefore probable that they do 

 not originate from any known existing form, but from an 

 extinct type closely approaching the ancestral form of 

 the Pyralidina, and now apparently most nearly repre- 

 sented by the Tineodidce. 



In the foregoing remarks no allusion is made to the 

 Alncitidce. The following is a sufficient definition of the 

 family characters : — 



