238 Dr. Max Weber on the 



during the day at a depth of half a metre to a metre beneath 

 the surface. In the present communication I shall be able to 

 add the description of a new Argulus to the descriptions of 

 Entomostraca already published. 



In opposition to the Entomostraca, Decapod Crustacea play 

 an important part in the islands of Sumatra, Java, Celebes, 

 Saleyer, and Flores visited by me. The number of species of 

 Brachyura which I collected in these localities has been 

 determined by Herr J. G. de Man to be thirty-four, and of 

 Macrura thirty-five. When compared with the freshwater 

 Decapods of Europe, which only include Astacus, Telphusa 

 Jluviatilis, Pilumnus tridentatus, Maitland, Hemicaridina 

 Desmarestu, Millet, Leander Edwardsii ) Heller, and Palcemo- 

 netes varians, Leach — the latter four of which are also found 

 in brackish water — as well as the cave-shrimp, Troglocaris, 

 the number of Decapods in the Indian Archipelago is very 

 considerable. Not only the number of species, but also that 

 of individuals, is very great in all lakes, ponds, rice-swamps 

 (Sawahpfutzen), and sluggish and rapid brooks and rivers, so 

 that they give quite a distinct impress to the fauna. It will 

 subsequently be shown in greater detail that genuine marine 

 and also brackish-water forms, especially among the 

 Brachyura, furnish their contingent not merely in the lower 

 courses of the rivers, but also further inland. 



Our sketch of the freshwater Crustacean fauna would, 

 however, be left incomplete if we omitted to mention a small 

 number of Amphipods and Isopods. It is true that these are 

 by no means conspicuous either on account of their numbers 

 or the frequency of their occurrence. They are, however, of 

 interest by reason of biological peculiarities, and throw an 

 important light on the origin of a portion of the freshwater 

 fauna of India, whereby perhaps they also afford some 

 elucidation of the origin of the tropical freshwater fauna in 

 general. 



In spite of extensive investigations of numerous fresh- 

 waters, I succeeded in discovering none but marine Amphi- 

 pods and Isopods therein ; and the exceedingly scanty 

 statements of my predecessors, among which, as a matter of 

 fact, the careful communications of von Martens are alone 

 deserving of mention, furnish the same result. Again in 

 opposition to Europe, to the fauna of which Gammaridae and 

 Asellidse belong, both of these families are wanting in the 

 Malay Archipelago. Here I found only the genus Orchestia 

 in Java, Celebes, and Flores, but solely in four localities in 

 spite of diligent searching, and, moreover, under such con- 

 ditions as proved that one of the species met with had already 



