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Show 586 DR. C SEMPER ON MACROBRACHIUM. [Nov. 26, omits this fact and simply mentions the Antilles as its home. In the British Museum are numerous specimens of different sizes from Brazil, the West Indies, Surinam, British Guiana, Bahia, and the Isles of Cape Verde. The specimens from Surinam and British Guiana came from fresh water. The only difference between the younger and smaller specimens and the larger ones is that the spines on the legs of the latter are replaced by tubercula ; besides they lack the two or three large teeth on the inside of the digits which are found in the extraordinarily large specimens from Lake Amatitlau. Even Milne-Edwards mentions, in his well-known handbook, that these teeth are exclusively found in the oldest individuals-a statement which seems to have escaped Mr. Spence Bate. Macrobrachium formosense, Spence Bate, is probably only a variety of the well-known Palcemon ornatus, Olivier. This species is found distributed from the East Indies, over the Malaccas and Philippine Islands, as far as Australia and the Fiji Islands in the Pacific. I found it myself only in fresh water in the Philippines. The specimens in the British Museum from the Fiji Islands and Australia are also from fresh water. 31acrobrachium lonyicliyitum, Spence Bate, I cannot at present identify with any species known to me ; it may therefore pass as a new species. 3Iacrobrachium africanum, Spence Bate, is one of those unfortunate creatures which nearly everv naturalist has declared to be new without even comparing it with other allied species. It is the old Palcemon gaudichaudii, Olivier, well figured by d'Orbigny *, 1843. Two specimens of this species with the original labels of Stimpson are in the British Museum ; and these, though smaller, so completely correspond with Mr. Spence Bate's original specimens from the Tambo River that their specific identity cannot be doubted. Poeppig-f* described (1836) the same species from the river "Aconcagua" in Chile, under the name of Palcemon ceementarius. His description is so careful and exact that no doubt can prevail. Later, Philippi J, having obtained the same species from the river "La Ligua" in Chile, founded upon it his genus Bithynis with the species longimana. The only distinction he could find between this new genus and Palcemon was the extremely short rostrum. On the other hand, Mr. Spence Bate, in setting up his genus Macrobrachium, attaches great importance to the long arms, but forgets that the species in question has shorter arms than other species of Palcemon (as, for instance, Palcemon carcinus, Fabr., which also lives in fresh water), and that between these species with very long and others with very short arms all possible transitions are to be found. Both gentlemen, however, entirely overlook another characteristic which seems to be of importance with regard to the subgenus Leander. It is the absence of a second spine behind or under the marginal spine of the thorax. If I remember right, Heller mentions somewhere that the species of the genus Leander, * Voyage clans 1'Amerique meridiem. &c, tome vi. p. 37, pl 17 fio* 2 t Archiv f. Naturgesch. 1836, Bd. i. pp. 143-145. X Archiv f. Naturgesch. 186U, Bd. i. pp. 161-164. |