380 IDOTEIDA. 
Idotea Bastert. Avpouin, Descr. of Savieny, Egypt. Crust. pl. 12, 
f. 6. Roux, Crust. Mediterr. t. 29, f. 1—10. 
Idotea tridentata. LaTreIiuy, Con. Crust. et Ins. 1, p. 64. Lamarcx, 
H. Anim. s. Vert. 5, p. 269. 
Idotea variegata. Rovx, Crust. Mediterr. pl. 30, fig. 1—9. 
Armida bimarginata. Risso, H. n. Eur. merid. 5, 109. 
Tuts large species has the body of a very elongate- 
oval form, slightly narrowed towards the extremity of 
the tail, which is terminated by a strong central point, 
having a smaller one on either side, which is, however, 
often wanting, and the lateral angles rounded. 
The lower antenne are nearly half the length of the 
entire animal, the first joint very short and scarcely 
visible from above; the four following joints gradually 
increase in length, but decrease in thickness, and the 
flagellum, which is rather longer than the five-jointed 
peduncle, is slender, and consists of about twenty articu- 
lations. The first segment of the body has the coxal 
plate fused at the sides, but the six following have it 
separated by a curved incision (indicating the epimeral 
or basal joint of the legs), and which is more angulated 
in the middle on the three posterior segments. The 
anterior segment of the tail in the male is armed beneath 
with two short horny points, directed backwards, and the 
second pair of the branchial plates is also furnished, in 
this sex (at least), with an elongated style, nearly as long 
as the plates. 
The tail consists, apparently, of four segments, of 
which the first and second are quite distinct, although 
very short, but the third loses all trace of articulation 
in the middle of the back, so as to appear completely 
soldered with the large terminal joint. 
This species varies greatly in its colours and markings ; 
generally, it is of a dirty greenish-grey, but often has a 
pale longitudinal line down the middle of the back, or 
