170 ANCEID. 
ISOPODA. ANCEID4. 
ABERRANTIA. 
Genus—A NCEUS. 
Gnathia. Luacu, Edinb. Encyc. (male). 
Anceus. Risso, Crust. des Nice, p. 51, 1816 (male). Drsm. 
Praniza. Luacu, MSS. Russo, Latr., Lam., Dusm. (female). 
Generic character. Male. Cephalon large, broad, quadrate. 
Pereion having the first two segments absent, or fused with the 
cephalon ;_ the two next separated from the three posterior. 
Pleon with six segments, the posterior terminating acutely. 
Eyes large and placed at the antero-lateral angle of the head. 
Antenne simple, subequal Mandibles anteriorly produced from 
the anterior margin of the cephalon. First gnathopoda wauting. 
Second pair of gnathopoda transformed into the outer appendage 
of the mouth. Pereiopoda subequal, the three posterior pairs 
reversed. Pleopoda biramose, posterior pair planted, on each 
side of the caudal segment. These are the characters of the 
animals long known only as Anceus. 
Female. Cephalon small, quadrate. ~ Pereion having the first 
two segments wanting or fused with the cephalon, the two suc- 
ceeding distinct, small, subequal; the three last fused together. 
Pleon as in the male. This character distinguishes the animals 
long known as Praniza. 
Tue history of this genus is so remarkable as to merit 
a detailed account. ‘The earliest record of one of these 
animals is contained in the microscopical work of Slabber, 
““ Natuurkundige Verlustigingen,” republished at Nu- 
remberg in 1775, under the title of ‘* Physicalischen 
Belustigungen,” 4ito, p. 37, pl. 9, where the author gives 
the representation, and ‘‘ Wahrnehmung eines Oniscus 
marinus,” being a satisfactory figure of a Praniza, which 
he had found on the shores of Holland, during four 
months of the year, in considerable quantities, and which 
exhibited great agility in the water. This figure was 
copied by Latreille in the great ‘‘ Encyclopédie Métho- 
