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Show 1892.] MR. F. E. BEDDARD ON THE INDIAN DARTER. 295 probably has, though I have not definitely made out the fact, a connection with the air-sacs. Osteology, and Comparison with Plotus anhinga. The osteology of the Darters has received attention from Brandt \ Eyton2, Donitz3, Garrod4, and Milne-Edwards5. The only one of these authors to describe and figure the species which is the subject of this communication is M . Milne-Edwards. The entire skeleton, as well as the separate bones, are figured in the magnificent work upon the Natural History of Madagascar, now in course of publication. Milne-Edwards, however, does not do much more than describe the osteology of Plotus melanogaster ; there is but little in the way of a comparison between this and other species. M y object in the present paper is to point out the principal differences between Plotus melanogaster and P. anhinga. I must first of all refer to an interesting matter concerning the skull, which has already been dealt with by Garrod for P. anhinga. In the figure illustrating the skull6, Garrod has indicated a small rod (lettered "a") attached to the occipital bone. Of this he writes as follows : - " In speaking of Phalacrocorax cristatus, Mr. Eyton remarks, the tubercle on the upper edge of the occipital bone has a pointed, movable, triangular process attached to it, which I suspect has also been the case with my specimen of Plotus, but has been lost." In the Society's female specimen there is a fibro-cartilaginous, similarly situated process, not more than one sixth of an inch long, which is ossified in the evidently older male. In his notes on the anatomy of the Cormorant, Hunter tells us that " a small bone, about an inch long, passes back from the os occipitis and gives origin to the temporal muscle, which is very strong." The same bone in the Darter, although comparatively not so long, performs the same function, the superficial temporal muscles meeting behind the skull along the median raphe, which becomes ossified to tbrm the above-mentioned bony style in the adult bird." This is not figured by Milne-Edwards, but I found the bone in Plotus melanogaster attached precisely as is figured by Garrod for P. anhinga. The bone was of a triangular form, thus resembling more closely the corresponding bone of the Cormorant. It was entirely ossified. In comparing the two skulls of P. anhinga and P. melanogaster, the process of the occipital bone to which the ossicle in question is attached is seen to have a truncated form in P. melano-gaster, whereas in P. anhinga it has, as Garrod has correctly figured, a more conical form, terminating in a point. 1 Mem. de l'Acad. Imp. de St. P6tersb. t. v. (1839). 2 Osteologia Avium, p. 218. 3 Archiv f. Anat. u. Phys. 1873, p. 357. 1 Loc. cit. 5 Histoire nat. de Madagascar, t. xii. p. 690. 8 Loc. cit. pi. xxviii. fig. 1. |