586 DR. C. SEMPER ON MACROBRACHIUM. [NoV. 26, 



omits this fact and simply mentions the Antilles as its home. lu 

 the British Museum are numerous specimens of diiferent 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 Amatitlan. 

 Even Milne-Edwards mentions, in his well-known handbook, that 

 these teeth are exclusively found in the oldest individuals — a state- 

 ment which seems to have escaped Mr. Spence Bate. 



Macrobrachimn formosense, Spence Bate, is probably only a variety 

 of the well-known Paltemon 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 speci- 

 mens in the British Museum from the Fiji Islands and Australia 

 are also from fresh water. 



Macrohrachium longidiyitum, Spence Bate, I cannot at present 

 identify with any species known to me ; it may therefore pass as a 

 new species. 



Mucrobrachium africamim, Spence Bate, is one of those unfortu- 

 nate creatures which nearly every naturalist has declared to be new 

 without even comparing it with other allied species. It is the old Pa- 

 Icemon yaudichaudii, Olivier, well figured by d'Orbigny*, 1843. Two 

 specimens of this species with the original labels of Stiinpson are in 

 the British Museum ; and these, though smaller, so completely cor- 

 respond with Mr. Spence Bate's original specimens from the Tambo 

 River that their specific identity cannot be doubted. Poeppigf de- 

 scribed (1836) the same species from the river "Aconcagua" in Chile, 

 under the name of Palcemon ccementarhis. 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 lonyimana. 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 Mucrobrachium, attaches great importance 

 to the long arms, but forgets that the species in question has shorter 

 arms than other species of Pa/cemon (as, for instance, Palcemon car- 

 cinus, 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 over- 

 look another characteristic which seems to be of importance with i-e- 

 gard to the subgenus Leander. It is the absence of a second spine be- 

 hind or under the marginal spine of the thorax. If I remember right, 

 Heller mentions somewhere that the species of the genus Leander, 



* Voyage dans I'Amerique meridion. &c., tome vi. p. 37, pi. 17. fig. 2. 

 t Archiv f. Naturgesch. 1S3(), Bd. i. pp. 143-145. 

 J Archiv f. Natui-gescb. 1860, Bd. i. pp. lGl-164. 



