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 G. — A Icironidce. 



Under this name are grouped three or four genera in 

 which the limbs of the pera^on never show the expansion 

 of the joints and fringing with seta3 which in the preceding 

 families often adapt those limbs to assist in the operation 

 of swimming. The fifth segment of the pleon has its sides 

 covered by the lateral angles of the fourth. 



Alcirona^ Hansen, 1890, has the clypeus (the shield-like 

 plate to which the upper lip is attached) large, crescent- 

 shaped ; the peduncle of the second antennae long ; the 

 first three pairs of limbs of the pergeon with the fifth joint 

 not produced on the inner side, the last four pairs with the 

 sixth joint not dilated. Alcirona Krehsii and Ahirona 

 insularis are described by Hansen. 



Lanocira, Hansen, 1890, has the clypeus small; the 

 peduncle of the second antennas short ; the limbs of the 

 peraeon as in the preceding genus. Lanodra Krbyeri^ 

 Hansen, is the type. 



Tachcea, Schiodte and Meinert, 1879, has the clypeus 

 small ; the peduncle of the second antennas long ; the first 

 three pairs of limbs of the peraeon with the fifth joint very 

 broad, produced on the inner side, the last four pairs with 

 the sixth joint dilated. To the type-species, Tachcea eras- 

 Hansen adds Tachcea incerta. 



Corildna, 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 erythrcea, 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^ Girolana, and 



