INTRODUCTION. ll 



The family of Gammakid^ belongs to the Arctic and 

 north temperate zones. With but few exceptions of the 

 closely allied congeners Dexamiyie 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 Aora 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, au 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 Nlphargus, 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 Nij)hargus. Of the two species of Cran- 

 gonyx, another fresh-water subterranean genus, one is 

 found in England, the other in Kamschatka, and these 

 bear a very 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 Tlie/i/a have been taken in European, Brazilian, and 

 Indian seas, and Moera 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 



