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Show 548 ON THE RUDIMENTARY HALLUX OF BIRDS. [June 20, Mr. Sclater also exhibited some Lepidopterous and other Insects which had been recently reared at the Insect-House in the Society's Gardens under the care of M r. A. Thomson. The following is a list of the species exhibited :- Attacus mylitta. cynthia. Samia cecropia. Cricula trifenestrata. Deilephila euphorbia?. Trochilium apiforme. melanocephaluin. Sciapteron tabaniforme. Sesia scoliiformis. • formiciformis. • conopiformis. musciformis. spheciformis. Argynnis paphia. Lycaena iolas. Mr. W . A. Forbes exhibited preparations showing the rudimentary hallux of several birds commonly described as three-toed, and made the following remarks :- "Whilst engaged in working out m y 'Report on the Anatomy of the Petrels' for the 'Voyage of H.M.S. Challenger,' I happened to come across Dr. Kidder's note ' on the existence of a rudimentary external hallux in Phabetria fuliginosa, a bird hitherto supposed, like other Albatrosses, to lack the hind toe altogether. Finding, on an examination of my specimen, his remarks correct, I proceeded to examine examples of three other species of Albatrosses that I had in the flesh, namely Diomedea exulans, D. brachyura, and Thalassiarche cul-minata. In all of these I discovered a hallux present, though in a most rudimentary condition, consisting of a single small nodule of bone, which lies altogether underneath the skin, in the fibrous subcutaneous tissues, and only appears externally as a minute pimple-like elevation, with no claw. In Phcebetria there is a minute claw visible externally, whilst internally two small bony nodules are discernible, representing undoubtedly the metatarsal element and the hallux, which, as in all other Tubinares, is reduced to a single phalanx. It is difficult at present to say whether the single nodule of the other Albatrosses represents these two elements fused together, or only one of them : in the latter case it is probably the phalanx itself that is wanting2. " The discovery of the rudimentary hallux in the Diomedeinae has led to finding a similar one in some other birds usually considered to be three-toed, namely the Woodpeckers of the genera Picoides and Tiga. In these the hallux consists of its normal number of phalanges, of minutesize, asisalso the metatarsal. The "great toe" thus formed lies completely under the skin, and is only discernible on reflecting the integuments carefully, when the chain of minute ossicles, connected to each other and to the tarso-metatarse by fibrous tissue, appears. " These facts render it not improbable that a similarly reduced hallux may really exist in many birds commonly described as three- 1 Bull. U.S. Nat. Mus. i. p. 22. 2 Cf. Voyage of H M.S. ' Challenger:' Report on the Anatomy of the Petrels, pp. 13, 14. |