li INTRODUCTION. 
shores of the Black Sea is as large and well developed 
as the Arctic specimens. From Pondicherry, also, a 
specimen is recorded that closely resembles the large 
specimens of the northern type. 
The genus Gammarus, even as we have restricted it, 
contains between forty and fifty species, all of which are 
Arctic and north temperate, and extends round the globe, 
except one taken at Jamaica, another at New Holland. 
Fresh-water species of the genus inhabit the rivers and 
streams of Europe and North America. Megamera, a 
near congener of Gammarus, has the largest and most 
spinose species in the northern regions, while others are 
found at Peru, Borneo, and the Zooloo seas. 
The genus Amphitoé contains between thirty and forty 
species, and is very universally spread over the globe, 
species having been taken in the Arctic seas and all round 
the coast of Europe, in the Black Sea, and the Medi- 
terranean ; they have been found at the Cape of Good 
Hope, and on the eastern and western coasts of South 
America, on the Australian shores, as well as in Zooloo 
and Japanese seas, in the islands of the Pacific and 
Atlantic Oceans, also on the weed in the Saragossa Sea, 
of the Atlantic, and on floating plants in the Pacific ; and 
one species is recorded from the fresh-water marshes of 
South Carolina. 
Podocerus is mostly northern, extending, however, 
down the coasts of Europe and America. One species is 
recorded by Dana from the Bay of Sunda, and another 
from the shores of Brazil. 
Cerapus, including its female, Leucothoé, has a wide 
range, species having been taken on the European and 
North American shores, on the eastern coast of South 
America, and in the Indian and Zooloo seas, while its 
near ally, Siphonecetus, has only been found on the north- 
