274 ISOPODA. 
whilst the third tribe, C. parasites, forms our restricted 
family CymMoTHoip#&, the species of which are parasitic 
on fishes, all their legs being alike in form and strongly 
hooked for prehension, they are all, as well as the 
antenne, short, and the latter are always inserted on 
the underside of the head, beneath a prolongation of the 
forehead, and the body is of a less firm consistence than 
in the dgide, thus approaching the Bopyride. The 
species are numerous, but chiefly inhabitants of Tropical 
Seas ; some few are, however, known to inhabit more 
temperate climes, but no specimen has hitherto been 
satisfactorily determined as having been found in our 
own seas, although Cymothoa Cistrum * is introduced by 
* Cymothoa, Fabricius, is distinguished from the other genera of this tribe 
or family by having all the segments of the pleon distinct and movable, the 
pleon itself considerably narrower than the terminal portion of the pereion, 
the last segment wider than long, and the legs tolerably strong and subche- 
liferous. 
Cymothoa Cistrum) is distinguished from the other species of the genus 
by having the anterior margin of the cephalon advanced and bent down 
between the inner antennz, which are inserted widely apart, the first segment 
of the body very large and advanced beyond the head on each side, and by 
the lower edge of the bases of the fourth pair of legs armed with a strong 
tooth. 
This species is found in the Atlantic Ocean and in the Seas of both Indies. 
Tt attacks fish, and makes occasionally large wounds sufficient to cause the 
death of the individuals attacked. 

* Oniscus Zstrum, Linn. Syst. Nat. pp. 1059, no. 2, Faun. Suec. no. 
2053. Mus. Adolph. Frid. 89. Fasricrus, 
Syst. Ent. p. 294. Sp. Ins. i. p. 375, no. 4. 
Pauuas, Spic. Zool., fasc. 9, p. 74, tab. 4, 
figs 13s) ACB: 
Cymothoa strum. Lracu, Edinburgh Ene. vii. pp. 405 and 433. 
Enc. Brit. Suppl. 1, p. 428. Trans. Linn. 
Soc. xi. p. 8372. Dict. Sc. Nat. t. 12, p. 853. 
Samovrttz, Ent. Compend. p. 109. Dks- 
MAREST, Cons. Crust. 309, pl. 47, figs. 6, 7. 
Mitne Erwarps, Hist. N. Crust. 3, 269. 
Régne An. (Crochard Edit.), Crust. pl.65,f.1. 
Asellus Zistrum. Ourvier, Ene. Méth. 4, 253. 
