the Geometrina of the Euyopcau Jaana. 55 



less development of the projecting scales or hairs clothing 

 the second joint ; the terminal joint is more or less 

 cylindrical and ohtuse, usually very short. The differ- 

 ences in the structure of the antennre are simple, hut 

 always of some importance, though not as a leading 

 character. As a general rule, where there are nearly 

 allied forms with pectinated and simple antennae, those 

 with the ]:ectinated antennae are the earlier. In the 

 fore wings vein let is usually very short, and in some 

 instances tends to be obsolete. Vein 1^ has normally 

 a well-marked basal furcation of moderate length, but 

 the lower branch of this fork is commonly much more 

 slender, and tends to be obsolete ; when there appears 

 to be no furcation, it is because this branch has become 

 (juite obsolete, and the result is never (as in the PyraJi- 

 dina) effected by the gradual shortening of the fork. 

 Vein Ic is obsolete. In the hind wings 1 c is also obso- 

 lete ; 1 a and 1 b are normally present, but in a few 

 instances, where absorption of the inner marginal area 

 has taken place, 1 a seems to be absent. Vein 8 has a 

 short but strong basal furcation. 



Although in external structure there are but few 

 characters available for generic definition (in comparison 

 with the Pi/raUdina, for instance), the neuration affords 

 abundant material. The structure of veins 5 and 8 of 

 the hind wings affords an easy means of separating the 

 grouj) into families which are at once highly natural and 

 easy to recognise. In the fore wings the remarkable 

 differences in the structure of veins 10 and 11 are of 

 considerable though inferior value ; here, however, care 

 has to be taken to eliminate the element of variability. 

 The tendency to anastomosis of these veins with one 

 another and with 9 or 12 is far more pronounced in this 

 group than in any other, though by no means confined 

 to it. The term anastomosis is used when two veins 

 meet, coincide for a short or long distance, and separate 

 again ; connection when two veins are united by a trans- 

 verse bar ; and I use the latter term also to include 

 those very frequent cases when the bar is so short as to 

 be reduced to a point, so that the veins appear to touch 

 at a point only ; this is of course, in fact, the inter- 

 mediate stage between connection and anastomosis. 

 Although in the following diagnoses I have kei)t these 

 two terms distinct, vet there is little essential difference 



