58 Mr. E. Meyrick on tJie classification of ■ 



the inner marginal area in forming the characteristic 

 lobes or pockets of that group. Even in this modified 

 form it is almost equally peculiar, though of course a 

 connecting bar nearer base is common. The constant 

 and uniform anastomosis of veins 9, 10, 11 of fore wings 

 also affords a very distinctive feature, equally absolute 

 though less exclusive ; it has the effect of producing a 

 constant auxiliary cell, which in the generic descriptions 

 of this family is termed the areole ; when 10 and 11 rise 

 separately, the resulting areole is double ; when they 

 are coincident towards base, it is simple. The com- 

 bination of these well-marked characters with the 

 ordinary structure of the Geoinetrina renders the family 

 particularly easy of recognition. Also, as in all cases 

 forms possessing the simple areole must necessarily 

 have originated in the first instance from forms with the 

 double areole (the reverse process is obviously im- 

 possible), and forms with the connecting bar in the 

 hind wings from forms with complete anastomosis (in 

 this case the retrograde change is certainly quite possible, 

 but not very probable, and I have not detected any 

 instance of it), considerable assistance is given towards 

 determining the order of development of the genera. 



The tongue is well-developed in all European genera, 

 and is therefore not specially mentioned. 



In one European genus (also in one or two exotics not 

 closely related to it, and I have recorded an instance 

 occurring abnormally in the case of one individual of an 

 exotic sjiecies)* the posterior wall of the areole is wholly 

 absent through obsolescence ; this causes the neuration 

 to appear very different, as it would seem that vein 7 is 

 quite separate from 8 and 9, whilst 10 seems to rise out 

 of 9, and 11 to anastomose with 9, or if the areole was 

 simple, to rise also out of 9. If this structure had only 

 occurred in a single instance, it would have been very 

 puzzling ; there is, however, no doubt that it has 

 originated in the way described, and it is particularly 

 necessary to have a right conception of the process, as 

 it would otherwise be an unaccountable exception to an 

 absolute character of the whole of the Geometrina. The 

 sudden disa[>pearance of a jjortion of a vein is still very 

 curious and unusual, and probably depends on some 

 physiological fact at present unappreciated. 



- Proc. Lion. Soc. N.S. Wales, 1890, 825. 



