348 A HISTORY OF RECENT CRUSTACEA 
the A‘gidz have the flagella of both pairs of antennz 
markedly distinct from the peduncles, and the earlier 
pleopods, the uropods, and the terminal segment of the 
pleon ciliated. 
Aga, Leach, 1815. The maxillipeds have seven joints, 
or at the least six. In the female with eggs, the first pair 
of marsupial plates are so large that they cover up all the 
parts of the mouth except the clypeus, part of the upper 
lip, and about half the ‘ palp’ of the mandible, thus leaving 
the animal incapable of taking food. In accordance with 
this condition, the ovigerous female, it is said, has never 
been taken upon a fish. 
Rocinéla, Leach, 1818. The maxillipeds are four- 
jointed ; the mandibles have the apex narrow, not denticu- 
late, and the second joint of the ‘ palp’ not much longer 
than the first. 
Alitrépus, Milne-Edwards, 1840. The maxillipeds are 
four-jointed. It is doubtful whether this genus should be 
separated from Rocinela. The descriptions of Alitropus 
typus, Milne-Edwards, and of Alitropus foveolatus, Schiédte 
and Meinert, do not supply characters for discriminat- 
ing it. 
jointed. The mandibles have the apex flattened and denti- 
culate, and the second joint of the ‘ palp’ shorter than the 
first. The type-species, Syscenus infeliz, Harger, is with- 
out eyes. 
In the ‘ British Sessile-eyed Crustacea,’ Bate and West- 
wood describe four species of Avga. The first is called Mga 
bicarinata, Leach, which must yield to the earlier name 
Aiga rosacea (Risso), a Mediterranean species, for the 
occurrence of which in Great Britain there is no definite 
authority. It is very hike Aga Strémii, Liitken, but dis- 
tinguished from it by much smaller and more widely 
separated eyes. It is now known that the specimen men- 
tioned by the above-named authors as sent them by the 
Rev. A. M. Norman from the coast of the county of Durham, 
was in fact an Afga Strémii with eyes contiguous. The 
second species Aga tridens, Leach, has also large eyes, 
Syscénus, Harger, 1878. The maxillipeds are four- 
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