170 ANCEID.E. 



ISOPODA. A NCEID^fl. 



ABERRANTIA. 



Genus— ANCEUS. - 



Gnathia. Leaoh, Edinb. Encyc. (male). 



Aiiceus. Risso, Crust, des Nice, p. 51, 1816 (male). Desm. 



Praniza. Leach, MSS. Risso, Late., Lam., Desm. (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. 

 Antennas simple, subequal. Mandibles anteriorly produced from 

 the anterior margin of the cephalon. First guathopoda wanting. 

 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 Anceiis. 



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. 



The 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," 4to, p. 37, pi. 9, where the author gives 

 the representation, and " Walirnehmung 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 " Encyclopedic M6tho- 



