346 A HISTORY OF RECENT CRUSTACEA 
which Leach is said to have framed without any meaning 
or derivation, but simply by placing in various positions 
the same four consonants, and interspersing vowels to suit 
the requirements of his ear. 
Family C.—Alcironide. 
Under this name are grouped three or four genera in 
which the limbs of the pereeon never show the expansion 
of the joints and fringing with setee which in the preceding 
families often adapt those limbs to assist in the operation 
ofswimming. ‘The fifth segment of the pleon has its sides 
covered by the lateral angles of the fourth. 
Alciréna, Hansen, 1890, has the clypeus (the shield-like 
plate to which the upper lip is attached) large, crescent- 
shaped; the peduncle of the second antenne long; the 
first three pairs of limbs of the perzeon with the fifth joint 
not produced on the inner side, the last four pairs with the 
sixth joint not dilated. Alcirona Krebs and Aleironu 
insularis are described by Hansen. 
Lanocira, Hansen, 1890, has the clypeus small; the 
peduncle of the second antennz short; the limbs of the 
pereon as in the preceding genus. Lanocira Kriyeri, 
Hansen, is the type. 
Tacheea, Schiddte and Meinert, 1879, has the clypeus 
small; the peduncle of the second antenne long; the first 
three pairs of limbs of the pereeon with the fifth joint very 
broad, produced on the inner side, the last four pairs with 
the sixth joint dilated. To the tvpe-species, Tachcea cras- 
sipes, Hansen adds T'achcea incerta. 
Coriléna, Kossmann, 1880, is incompletely described, 
but is remarkable by having on the very short first pair of 
limbs the claw as long as the other joints together. The 
type-species, Corilana erythrea, is from the Red Sea, and 
was established from a specimen only an eighth of an inch 
long. 
In addition to the six species of Alcironidae already 
mentioned, five or six more may in fact belong to this 
family, rather than to the genera ’ga, Cirolana, and 
