15-1 ' [December, 



length of the ultimate joint," whereas, in Gredemnon, is is said to be 

 "longer than" that joint. 



In Cerostoma the ocelli are present, in Credemnon they are said to 

 be absent, as also in the allied genus Periclymenobius. 



My assistant, Mr. Durrant, in examining the structure of some 

 North American species, found that ocelli were present in all, and 

 suspecting that Wallengren's observations on this point were incorrect, 

 we carefully examined all the species mentioned in his paper. The 

 result has been the discovery, that contrary to the statements of that 

 author, ocelli are present not only in the genera Cerostoma and Tra- 

 choma, but in Gredemnon and Periclymenobius, as well as in Theristis, 

 where he had also failed to observe them. 



In defining the genus Credemnon, Wallengren writes that the 

 " carpal," or apical, vein of the fore-wings is " most often simple, 

 rarely stalked." In this genus he places three species, C alpellum, F., 

 O. lucellum, F., and C. sylvellum, L. Of these I find the first two only 

 have the apical vein usually simple, the last has it usually stalked. 

 Under Cerostoma, of which he writes that the apical vein is " simple 

 or forked," he tabulates four species, C. seqicellum, L., C. vittellum, L., 

 C. radiatellum, Don., and G. parentJiesellum, L. (= costellum, F.). , 



Of these I find the last two only have the apical vein usually 

 stalked. It is thus evident that we cannot separate Gredemnon on the 

 ground of neuration, and after correcting the error as to the absence 

 of ocelli, it seems impossible to attach generic value to the other dis- 

 tinguishing character claimed for it — "fringes of the fore-wings 

 drawn out to a short point at the anal angle." Thus, after recognising 

 Trachoma, Wlgrn., and Periclymenobius, Wlgrn., as possibly good and 

 distinguishable genera, there remains a large group of species for 

 which the lines of separation proposed by Wallengren are not suffi- 

 ciently satisfactory. I first endeavoured to arrange these in two 

 divisions according to the form of the apical vein of the fore-wings, 

 and the attempt led to the critical examination of this character in a 

 number of specimens. I was somewhat surprised to find that although 

 not unfrequently regarded as of generic value, it cannot be relied 

 upon as constant, if observed in few specimens only of each species, 

 and that it is necessary to examine a considerable series to ascertain 

 in each case what is the normal arrangement of the apical veins. 



The following table will serve to illustrate this assertion. It 

 shows the number of specimens of each species examined, and the 

 varying positions of the apical and sub-apical veins of the fore-wings, 

 as well as the proportion in which each variation occurs throughout 

 the series : — 



