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Show 1871.] MR. A. G. BUTLER ON ANGOLAN BUTTERFLIES. 721 which may furnish one with a clue to the reason for the existence of this osseous covering, whether such is for protection or whether a part of the auditory apparatus. Of the twenty-four Indian genera adverted to, we find some residents in waters of the plains, also in rivers on the hills with or without alpine sources. Amongst the seventeen resident in waters of the plains and not extending their range into hilly regions we find in seven the air-vessel is free, viz. in Rita, Hara, Pseudeutropius, Macrones, Callichrous, Wallago, and Pangasius; whilst in ten it is more or less enclosed in bone, viz. Ailia, Ailiichthys, Sisor, Bagarius, Saccobranchus, Silundia, Eutropiichthys, Gagata, Clarias, and Hemipimelodus. Amongst those residing in rivers of the plains and extending their range into those of the hills which have or are destitute of alpine sources, we perceive as follows :- Of those four genera which are found in the waters of the plains as well as in hill-rivers with alpine sources, all have their air-vessels enclosed in bone, viz. Amblyceps, Pseudecheneis, Exostoma, and Glyptosternum ; whilst the last three genera have representatives in the next division, and all are furnished with an adhesive apparatus. Of the three genera found in rivers of the plains and also in those of hills destitute of alpine sources, none have their air-vessels enclosed in bone, viz. Silurus, Olyra, Akysis. From the foregoing it appears that the majority of the genera of Indian freshwater Siluroids have their air-vessels enclosed in bone; That no true Indian, wholly marine Siluroid has its air-vessel enclosed in bone; That amongst the Siluroids of the hilly regions, those which ascend rivers having alpine sources have the air-vessel enclosed in bone ; That those which ascend rivers not snow-fed do not appear of necessity to have their air-vessels thus protected. Space and time will not permit m e to enter further on this subject at present, which, however, I hope to do at no very distant date. 2. O n a small Collection of Butterflies from Angola. B y A . G . B U T L E R , F.L.S.. F.Z.S., &c. [Eeceived November 8, 1871.] The present collection, though it only contains twenty-four species, of which three are new to science, is interesting as an addition to our knowledge of the Butterflies of Angola; it was made at Loanda, the capital of the Portuguese settlements in Angola, situated at 1000 feet elevation, at between 8° and 9° S. lat. Fourteen of the species in the following list were also in m y list of the Diurnal Lepidoptera taken by M r . Ansell at Kinsembo. This collection has been lent to m e for determination by m y friend and brother lepidopterist R. Meldola, Esq. |
