MIERS AND HARGER 375 
is an instance of the group in which the flagellum of the 
second antennz is rudimentary. Sars remarks that in his 
opinion ‘ Harger’s genus Synidotea [1878] should for the 
present be retained for the two Arctic species S. bicuspida 
and S. nodulosa {(Kréyer)], both differing distinctly from 
‘the form described by Guérin-Méneville—Edotia tuber- 
culata—in the well-developed, multiarticulate flagellum on 
the second pair of antennee.’ 
Cleantis, Dana, 1849, is distinguished by the flagellum 
of the second antennz being all fused into a single piece, 
but even this character is sometimes shared by Idotea 
prismatica. The pleon in Cleantis may consist either of 
one, two, three, or five distinct segments. The New 
Zealand species, Cleantis tubicola, Thomson, is eleven times 
-as long as itis broad. Mr. Chilton is disposed to regard 
it as normally not a tube-dweller, though the type-speci- 
men was found in a tube. The species with all the seg- 
ments of the pleon fused, such as Cleantis filiformis (Say) 
from the United States, were referred by Dana and Harger 
to a separate genus, Hrichsonia, Dana, 1849. 
On this family the work by Miers already mentioned 
and Harger’s ‘Report on the Marine Isopoda of New 
England and adjacent waters’ are essential to the student 
for the groundwork of his inquiries. 
