224 AUSTRALIAN AND POLYNESIAN LAND AND MARINE MOLLUSCA, We have in this jaw a diastema unlike that of any known inacropod, but having its greatest similitude in Sthenurus. It is in the latter genus again that we find some approach to the greatly dilated incisor in the mandible before us. It has already been observed that the symphysis is that of Sthenurus rather than of Macropus on the one hand, or of the more aberrant macropod, Procoptodon, on the other. Concomitant with these indications of alliance with Sthenurus, we find however, a premolar departing from all others of the family. It seems, therefore, reasonable to surmise that Palorchestes was on the whole a true saltigrade of the macropodal type, and that the point of divergence whence its differentiation commenced, was Stlienurus or some form closely allied to it. The use to which the determination of such relation-ship may be put, is best known to those who have to deal with the disconnected bones of the numerous extinct species of kangaroos; without its guidance their identification, always doubtful in some degree, becomes the most unsatisfactory guess-work. Synonymy of Australian and Polynesian Land and Marine Mollusca. By J. Brazier, C.M.Z.S., &c, &c. 1. Patella aculeata. Patella aculeata, Reeve, Conch. Icon., pi. 32, sp. 90. ,, squamifera, Reeve, Coc. cit , sp. 94. ,' aculeata, Angas, Proc. Zool. Soc, p. 221, 1867. „ squamifera, Angas, loc. cit., p. 221, 1867. ,, aculeata, Tenison-Woods, Proc. Roy.Soc.Tas., p. 22, 1877, Bab. — Port Jackson near the Heads, and outside from the Clarence River on the north, to Twofold Bay on south ; it is also found in Tasmania. I have had some hundreds of specimens of the so-called species squamifera, but I can only identify them with aculeata. The very rough sculptured variety is of very common occurence at tho Old
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