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year 1888 the genus Synalpheus was created by Spence Bate, in the Report on the Macrura 

 collected by the Challenger Expedition, for a species which he thought to be new, but which six 

 years before had already been described by Haswell under the name of ^. Comahdaruvi: in 

 spite of the creation of this genus, several other species which also belong to this quite natural 

 o-roup, were erroneously referred by Spence Bate to the old genus Alphens. In his important 

 and masterly treatise on the Alpheidae published in 1899, Professor Coutiere has finally 

 definitively established the characters by which the genus Symalpheits is differentiated from the 

 other genera of the family Alpheidae. 



Of the genus Synalpheus no less than 38 species and 9 varieties have been collected 

 by the Expedition of the "Siboga", of which 22 respectively 7 proved to be new to science! 

 The total number of species of Synalpheus recorded from the Indopacific region therefore now 

 amounts to 62 species and 15 varieties. Of the 16 old species and the 2 old varieties, that 

 were collected by the "Siboga", two, viz. Syn. Charon (Heller) and Syn. Nilandensis Cout., are 

 apparently distributed through the whole Indopacific : the first, indeed, which was discovered in 

 the Red Sea, has also been taken near the Hawaiian Islands, the other, at first recorded from 

 the Maldive and Laccadive Archipelagoes, occurs also at the Mangarewa Islands, in the Pacific. 

 Syn. amboinae (Zehntner) and Syn. cariiiattis (de Man) were still only known from Amboina, as 

 was likewise the case with Syn. demani Borr., but the latter has also been observed at the Loyalty 

 Islands; Syn. Pococki has also a limited distribution, for this species was only known from the 

 eastern parts of the Archipelago as far as the Holothuria Bank, N.W. Australia and Torres Straits. 

 Eight species and two varieties are also found westward from the East Indian Archipelago, but 

 are not yet observed eastward from it. These species are the following: 



Syn. Gravicri Cout. 



Syn. hcroni Cout. 



Syn. neonieris (de Man) 



Sy7i. streptodactylus Cout. 



Syn. acantJiitelsonis Cout. 



Syn. liastilicrassus Cout. 



Syn. hiinidomafms Cout. 



Syn. binng2iiculatus (Stimps.) Cout. 



Syn. JVilandensis Cout. var. oxyceros Cout. 



Syn. paraneonieris Cout. var. prolatiis Cout. 



According to Coutiere, Syn. Gi-avieri should also exist in the China Sea, but the 

 occurrence of Syn. neonieris in Japan and in the Pacific is, in my opinion, still doubtful. One 

 species, Syn. neptitmis (Dana), occurs also in the Pacific and Syn. Pescadorensis Cout., that 

 inhabits the Pescadore Islands near Formosa, has also been captured in the Maldive and 

 Laccadive Archipelagoes. The two varieties, finally, Syn. Nilandensis Cout. var. oxyceros Cout. 

 and Syn. paraneonieris Cout. var. prolatus^ are distributed in the northwestern part of the 

 Indian Ocean. 



With regard to the range of the 24 old species and the 6 old varieties which were not 

 collected by the "Siboga", the following may be remarked. Syn. Coniatularum (Hasw.) inhabits 

 the Albany Passage near Cape York and Thursday Island, like also Syn. Haddoni Cout., a 

 remarkable species of which it is still doubtful whether it belongs to the Biunguiculatus or to 

 the Laevimanus group. Syn. Stimpsoni (de Man) is only known from Amboina, and Syn.Jielleri 

 de Man only from the Nicobar Islands, while Syn. Bakeri Cout. var. Storini n. has still onl)- 



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