INTRODUCTION. h 
The family of Gammarip# belongs to the Arctic and 
north temperate zones. With but few exceptions of the 
closely allied congeners Dexamine and Atylus, which 
consist together of twenty-one species, we know of only 
one taken, near Valparaiso: all the rest are northern 
species. Of the genus dora but two species are known; 
one from the British seas, the other from the western 
coast of South America (Valparaiso). Judging from the 
figures in Gay’s “ Hist. de Chile,” the resemblance of the 
two species is remarkably close, an apparently useless 
tooth on the anterior margin of the first pair of legs 
of the southern form alone distinguishing it from the 
northern. 
The subterranean fresh-water genus Niphargus, which 
lives generally in closed pump-wells in England and 
many parts of Europe, has its nearest congener in 
Eriopus, from the deep sea off Bohusia. Judging by the 
figure given by Bruzelius, there is little that distinguishes 
one genus from the other; and it is highly probable that 
Gammarus pungens, from the warm springs of Italy, is 
also a species of Niphargus. Of the two species of Cran- 
gonyx, another fresh-water subterranean genus, one is 
found in England, the other in Kamschatka, and these 
bear avery close resemblance to the female form of the 
marine Gammarella, a genus, though only having three 
species, found in the European seas, as well as on the 
South American coast and at Pitt’s Island. Species of the 
genus Melita have been taken in European, Brazilian, and 
Indian seas, and Mera extends all over the temperate zones 
of both Northern and Southern Hemispheres. The genus 
Amathia is essentially an Arctic form, the species losing 
their size and spinose character as they approach the 
temperate seas. No species has been recorded south of 
the English Channel, while a species found on the Crimean 
