272 A HISTORY OF RECENT CRUSTACEA 
The Greenland species, Mysis oculatus (O...Fabricius), is 
of special interest on account of the variety relicta, Lovén, 
found in great hordes in several of the large freshwater 
lakes of northern Europe, descended, it is supposed, from 
ancestors which occupied those regions when the waters 
were still salt and in connection with the open sea. In 
Mysis relicta the antennal scale is elongate, ciliated all 
FIG. 22.—Mysis relicta, Loven, s 
the first maxilla [Sars]. 
Fig. 23.—Mysis relicta, Loven, the second maxilla. 
round. Norman has obtained it from Lough Neagh in 
Ireland, and by this discovery provides the genus Mysis 
with at least one representative in the British fauna, after 
despoiling it of all the rest. Sars, in his ‘ Histoire des 
Crustacés d’eau douce de Norvége, has given a most 
elaborate description of this species, illustrated by highly 
finished and most instructive plates, and more recently it 
has been studied by Hansen with his accustomed acute- 
ness. The accompanying figures in the text are copied 
from Sars. Others from the same author are given in 
Plate XIII. on a reduced scale. 
Macropsis, ‘the long-eyed,’ is the only other genus 
agreeing with Mysis in the characters of the pleopods of 
the male, and it is distinguished from Mysis both by the 
extremely elongate eyes and by the structure of the first 
antennee, which, in addition to the two flagella and the 
setose appendage usual in the males of this family, have 
the apex of the peduncle armed with yet a fourth process, 
