CRUSTACEA. 



117 



Anceus (Pranisa) ceruliata. — Desmarest, Consid. sm. Crust., p. 284. 



This is the female, probably, of Anceus maxillaris. 



These two animals for a long time were considered as repre- 

 senting two distinct genera, and by some as separate families, 

 their habits and appearance are so unlike each other. It now 

 appears from the researches of M. Hepe, of Brest, who has the 

 honor of first determining their relative connection with each other 

 to be male and female. In early life the two resemble each other 

 very closely, and they then live as parasites on the external surface 

 of fish ; as they grow older the male assumes the form of Anceus, 

 and the female continues unaltered in the form of Pranisa. After 

 quitting their parasitic mode of life they appear, as far as we 

 can judge, particularly the male, to live without eating, for it 

 has no mouth, and the mandibles are placed in the front of the 

 head like antennae. The female appears to exist as a huge ovi- 

 sac, and when the young are matured the mother appears to be 

 empty, and almost devoid of the traces of internal organs. The 

 life of both male and female now appear, as far as usefulness is 

 concerned, to be over, for although I have kept them alive for 

 months in this condition they never appear to change, or seek or 

 obtain food, but lie motionless and feeble. 



ISOPODA NOEMALIA. 



B0PYRID2E. 



Genus, Bopyrus. — Latrielh. 



Male. Small, narrow ; antenna) rudimentary. 

 Female six times as large as the male. Pearshaped, unsymet- 

 rical. Body much flattened. 



Bopyrus squillarius. — Latriellc, Hist. Nat. Crust., vii,p. 55, t. 59, 

 /. 2. — Bate and JFestivood, p. 218. 

 Frequently found under the shell of prawns and shrimps. 

 From Polperro and off the coast. 



Genus, Piiryxus. — RathTce. 



Male. Vory minute and elongated, head transversely minute, 

 with two dark minute eyes. 



Female. Large inert nearly globular mass, with the segments 

 scarcely indicated by depressions, with w ide and oviparous plates. 



