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Show 1894»] ON THE ANATOMY OF ATHERURA AFRICANA. 675 ' that the gill-membranes are united to the isthmus, not forming a fold across it."_ But this character is not always constant. The museum of Christiania has three specimens of A. acipenserinus, received through the kindness of Dr. Gilbert from the Stanford "University, Cal. In two of these the gill-membranes form a short but distinct fold across the isthmus; in the third it is hardly perceptible. In A. gilberti some of the specimens show a trace of a similar fold, whilst in others the isthmus is smooth. A. decagonus, Bl. Schn. 1801, forms another transitional stage between the last group and the other, in which the gill-membranes form a distinct fold across the isthmus (as in A. cataphractus). In the first species the fold is always present, but very short. Consequently Podothecus can hardly rank as a genus, but forms in the typical genus Agonus a group of species which, by the structure of the snout and the dentition, may be separated from all Agonidce. Christiania, Oct. 1894. 5. O n the Anatomy of Atherura africana compared with that of other Porcupines. By F. G. PARSONS, F.R.C.S., F.Z.S., F.L.S., Lecturer on Comparative Anatomy at St. Thomas's Hospital. [Received October 12,1894.] The specimen of Atherura africana from which the accompanying notes were made was kindly placed at my disposal by Mr. F. E. Beddard, Prosector to the Society. I was induced to make a rather more exhaustive examination of certain parts of it than I otherwise might have done because I hope that some day I may have the chance of dissecting its Eastern relative, Atherura macrura, and of comparing the anatomy of the two. Professor Mivart's account of the anatomy of Erethizon dorsatum was of great value in comparing Atherura with the Tree-Porcupines; but I was unable to find a complete account of a dissection of a Ground-Porcupine, and am indebted to Professor Stewart for the gift of a spirit-specimen of a young Hystrix cristata, which I dissected pari passu. I am also indebted to Professor Howes and to Mr. Oldfield Thomas for their kindness in allowing me the use of their osteo-logical collections. OSTEOLOGY. The skull of Atherura has already been described by Grayl and by Giinther2. The former gives the chief characteristics of it and 1 P. Z. S. 1847, p. 104. 2 P. Z. S. 1876, p. 743. 45* |