376 MESSRS. DIXEY, BUKR, XND PICKAKD-CAMBEIDGE OS [MaV 3, 



subconical, and only slightly separated by the black-coloured veins. 

 (3) All the black markings of the upperside are highly developed, 

 especially the submarginal band of the hind wing, which encroaches 

 considerably inwards. In the presence of the chain of small 

 median dark spots and in the large size of the fulvous submarginal 

 spots of the hind wing, B. hoydi approaches B. ilithyia ; in other 

 respects it is much nearer B. yotzius. The combination of 

 characters above given renders the Socotran form easily recog- 

 nizable among its allies, and seems to justify its separation as 

 distinct. I have given it the name hoydi, after the Principal 

 of Hertford Colleg3, to whom Science in Oxford is under great 

 obligations. 



" V^ery common everywhere, hills and plains. Not conspicuously 

 gi'ound-haunting." — E. N. B. 



Remarks on Geographiml and Seasonal Forms in the Genus Byblia 

 JJiibn. — Byblia gotzins Herbst { = Hypanis acJieloia Wallengr. ; 

 = H. ilithyia var. A, Trimen, S. Afr. Butt. vol. i. 1887, p. 264) is 

 probably entitled to distinct specific rank beside B. ilithyia Drury\ 

 Each form, as pointed out by Trimen (loc. cit. p. 266) and by 

 Barker (Trans. Ent. Soc. Lond. 1896, p. 415), has its own range of 

 seasonal variation. This is also shown by good series of both the 

 ilithyia and the yotzius (or acheloia) forms m the British Museum 

 and in the Hope Collection at Oxford. Eor a large proportion of 

 these each collection is indebted to Mr. G. A. K. Marshall, whose 

 specimens all bear such ajnple data with regard to locality, altitude, 

 and exact time of capture, as to throw much light upon questions 

 of local and seasonal modification. 



The geographical distribution of the two forms is interesting. 

 The ilithyia form, with some local variation in size and in the 

 relative proportions of dark markings to fulvous ground-colour, is 

 found in India, Ceylon, Arabia, and the greater part of Wallace's 

 "East African" subregion, including the West African coast dis- 

 tricts lying northwards from the Eiver Gambia and southwards 

 from the Congo. It also extends for some distance into the South 

 African subregion, occurring commonly in the Transvaal and Natal 

 highlands, and coming, though rarely, down to the sea at Durban. 

 Its distribution is therefore mainly Indian and " East African " in 

 Wallace's sense '". The gbtzius form, on the other hand, is absent 

 from India and from a large portion of " East Africa." It is found 

 at Sierra Leone, Cape Coast Castle, Lagos, Old Calabar, and the 

 coast districts of the Gaboon and the Congo ; but outside the limits 

 of Wallace's West African subregion, i. e. in Senegal to the north 

 and Angola to the south, it is replaced by typical ilithyia. Begin- 

 ning again on the south-east coast, about the easternmost districts 



' The evidence on which Mr. Marshall decides figainst their specific distinct- 

 ness appears to me to require confirmation. See Marshall in Ann. Mag. Kat 

 Hist. 1896, xviii. p. 338. 



- Wallace, 'Geographical Distributiou of Animals," 1870, ^ol. i. pp. '2bl, 

 '2c8 and map. 



