( cxxii ) 



forming an irregular reticulum. The central ribs, generally to 

 the number of six, are prolonged through the median consti-ic- 

 tion of the lamina into the distal portion, where they diverge, 

 afterwards converging slightly towards the distal extremity of 

 the lamina. These chitinous ribs are connected by means of a 

 clear interstitial membrane, which in the distal poi-tion is not 

 interrupted by cross-pieces or other visible structure. The 

 extreme tips of the ribs are free. The disc is clear, usually 

 triangular and apparently bilobed. 



It is not easy to bring the structure of these remarkable 

 bodies into relation with that of the usual type of plume- 

 scale. It may however be plausibly conjectured that the 

 chitinous ribs, though comparatively few in number, and 

 somewhat irregular in disposition, are homologous with the 

 similar structures to be observed more or less distinctly in the 

 scent-scales of many other genera. The distal portions of the 

 ribs, or their free extremities, may conceivably cori'espoiid 

 more or less exactly with the fimbriae of the ordinary plume- 

 scale, which in many cases appear to be simple prolongations 

 of the intra-laminar libs. It is worthy of note that among 

 the ordinary scales of most, perhaps all, of the species of 

 African Mylothris, some occur of a peculiar shape ; being 

 nearly rectangular and provided with sharp proximal 

 spines. These peculiar scales often exhibit a row of distal 

 projections, caused by protrusion of the ribs beyond the 

 general border of the scale. So far as my observations extend, 

 these scales are confined to the male sex. They certainly 

 suggest comparison with the curiously specialised scent-scales 

 of the genus. 



With regard to specific differences within the limits of the 

 genus, there is not much to be said. The median constriction 

 of the lamina is very slight in M. jacksoni, less slight in 

 J/, bernice and M. rubricosta, moderate in M. chloris and 

 M. 7'uppellii, and strongly marked in Jil. agathina, M. 

 pldleris and M. ^^oppea. The base in all the forms is angular 

 rather than rounded ; in those species where the constriction 

 is best marked, the proximal portion of the lamina is broad- 

 ened at the base. J/, pojipea may have indications of basal 

 cornua, The ribs in some species are beaded ; this is very 



