GENUS CASTNIA AND SOME ALLIED GROUPS. 159 



apparently only three branches, and tlie postcostal vein only five branclies ; the two 

 intermediate branches, namely the 6th branch of the postcostal (6 5*) and the 4th 

 branch (c 3*) of the median veins, have been assumed to be distinct from those veins, 

 and to constitute the remains of a vein intermediate between the postcostal and the 

 median, of which the basal portion has been aborted or seen only in a fold running 

 towards the base of the wing between those two veins. To these two detached branches 

 Mr. Doubleday applied the names of the Ist or upper discoidal nervule, and the 2nd 

 or lower discoidal nervule ; the little transverse veinlet connecting the 5th branch of 

 the postcostal vein with the upper discoidal nervule he termed the upper disco-cel- 

 lular nervule; that connecting the upper and lower discoidal nervules together he 

 termed the middle disco-cellular nervule ; and that connecting the fourth median (or 

 lower discoidal) nervule with the third branch of the median vein he termed the lower 

 disco-cellular nervule (these three disco-cellular nervules closing the discoidal cell) ; the 

 longitudinal fold or obsolete vein between the bases of the postcostal and median veins 

 within the discoidal cell, he termed the discoidal nervule. 



Erom the very great number of specimens of Lepidopterous insects of all families, 

 both diurnal and nocturnal, which I have examined, I prefer to treat the flrst or upper 

 discoidal nervule as part of the system of the postcostal vein and the second or lower 

 discoidal nervule as portion of the median system. But in order to mark the distinction 

 between these two aberrant nervules or branches and the true branches, or veinlets, or 

 nervules of the postcostal and median veins, I have, in the Plates of details of structure 

 illustrating this memoir, distinguished the upper or first discoidal nervule with the mark 

 b 5*, and the lower or second discoidal nervule as c 3*. 



In thus differing from the system of venation proposed by the late Mr. Edward 

 Doubleday in his paper on Argynnis, published in the ' Linnean Transactions,' and in 

 the introduction to the ' Genera of Diurnal Lepidoptera,' I cannot but admit the propriety 

 of the adoption of the stems of the veins as of primary importance — contrasted with the 

 plan of Herrich-Schaffer and other German writers, who seem to regard the branches as 

 of primary value, counting them (quite independently of their origin from the stems) 

 numerically upwards from the anal angle, from 1 to 12 : — No. 1 being the anal vein 

 (my d) ; Nos. 2, 3, 4 the three branches of the median vein ; 5 and 6 the two disco- 

 cellular veius (or my c 3* and b 5*) ; 7, 8, 9, 10, 11 the five branches of the postcostal 

 vein, and 12 the costal veinf. 



Many years ago I had a long controversy with the late M. Alex. Lefebvre on this 

 subject, in consequence of his adoption of tlie principle that the fold indicating the vein 

 in the discoidal cell of the fore wing, and ranning thence towards the outer margin, 

 formed the true line of demarcation between the branches of the postcostal and median 

 veins. The fold in question is, of course, the representative of the discoidal vein ; and an 

 examination of the figures accompanying tliis memoir, or those of Herrich-Schaffer's 



t InHs elementary plate, H.-SchafFer omitted one of the branohes of the postcostal vein, and so gave only 11 ribs 

 (as h.e terms the brancbes). Assmann (Schmett. Schles. tab. A. f. 1) counts the " Adern" of the fore -n-ing from 1 to 14. 

 adding the two snpplemental anal veins, which are sometimes, although very rarely, to be observed. 



