22 CRUSTACEA CHAP. 
Talitrus sylvaticus 1s very common among fallen leaves and 
decaying timber in Tasmania and Southern Australia, many 
miles from the sea, and often at an elevation of several thousand 
feet. 
Among the Gammaridae, certain genera, e.g. Macrohectopus 
(Constantia), from Lake Baikal, are purely fresh-water. An 
enormous development of Gammaridae was discovered by Dybowsky 
in Lake Baikal, comprising 116 species, and lately a number more 
have been found by Korotneff! The majority of these were 
originally placed in the genus Gammarus, but Stebbing has rightly 
created a number of peculiar genera for them. Certain species 
are, however, placed in more widely distributed genera, e.g. Gam- 
marus and Carinogammarus, which is also represented in the 
Caspian Sea. Korotneff found some remarkable transparent pelagic 
forms (Constantia) swimming in the abyssal regions at about 
600 metres depth, the majority of them being blind, but some 
possessing rudimentary eyes, often on one side only. 
Besides various species of Gammarus, a number of other 
Gammaridae are frequently found in brackish water. Among 
Haustoriidae Pontoporeia has representatives in both the oceans. 
and inland lakes of the northern hemispheres (see p. 137). 
Of the Decapoda, seven famihes are typically fresh-water in 
habitat—the Aegleidae, containing the single species Aeglea 
laevis, related to the Galatheidae, which inhabits streams in 
temperate 5. America; the Atyidae, a family of Prawns from 
the tropical rivers and lakes of the New and Old World, and in 
the Mediterranean region. A number of Palaemonidae are 
found in fresh water, e.g. Palaemonetes varians in Europe and 
N. America, while several species of Palaemon occur in lakes, 
streams, and estuaries of the tropical Old and New World. 
The expeditions of Moore and Cunnington to Lake Tan- 
ganyika brought back an exceedingly rich collection of Prawns, 
comprising twelve species, all of which are peculiar to the lake,” 
and this is all the more surprising since Lakes Nyasa and 
Victoria Nyanza are only known to contain one species, Caridina 
nilotica, which ranges all over Africa and into Queensland and 
New Caledonia. The Tanganyika species, however, all belong to 
purely fresh-water genera, and do not afford any suggestion 
1 Arch. Zool. Exp. (4), ii., 1904, p. 1. 
* See Calman, Proc. Zool. Soc. 1906, p. 187. 
