ME. E, J. MIEBS ON THE IDOTEID^. 21 



The following cliaracters will apparently suffice to distinguish 

 the species referred to this section: — 



* Terminal segment loicler at base than tlie preceding segments. 

 Terminal segment subtriangulate, with the angles rounded. 



1. I. Whymperi, Miers. 



** Terminal segment not wider at hase than the preceding. 

 Bounded at the distal end. 2. I. prismatica (Eisso). 



Feebly" emarginate at the distal end. 



3. /. mediterranea (E-isso), 

 Subangulated at the distal end. 4. I. Danai, Miers. 



Idotea peismatica. 



Zenobia prismatica, Risso, Hist. Nat. Eur. mericl. v. p. Ill, pi. v. 



fig. 24 (1826) ; Lucas, Anim. artic. in Expl. Sci. Algerie, p. 63 



(1849) ; Hope, Cat. Cr. Ital. p. 27 (1851). 

 Idotea cLelipes, Costa, Faun. Reg. Napoli, Cr. pi. xi. fig. 2 (1838); 



Hope, Catal. Crust, p. 26 (1851) ; nee Fabr., nee Latr. 

 Idotea prismatica. Heller, Verh, zool.-bot. Gesellsch. Wien, xvi. p. 729 



(1866) ; Stalio, Att. Istit. Venet. (ser. 5) iii. p. 1354 (1876-77). 

 Idotea parallela, S. Bate Sf Westwood, Brit. Sessile-eyed Crust, ii. 



p. 391, fig, (1868) ; Stebbing, Rep. Devon Assoc, vi. p. 772 (1874). 



The body is convex, narrow, and elongated, with the sides 

 parallel and the dorsal surface smooth. Head with its ante- 

 rior margin nearly straight, but feebly emarginate in the middle. 

 First thoracic segment with small rounded antero-lateral lobes 

 which do not reach to the eyes; all the thoracic segments with 

 their anterior and posterior margins nearly straight, their postero- 

 lateral angles rounded in the first three segments, and not at all 

 produced in the following segments. Postabdomen with four 

 distinct segments, the three first very short, the fourth nearly 

 twice as long as broad, with lateral sutures indicative of a coales- 

 cent segment near its base, its distal extremity semicircularly 

 rounded and entire, and the dorsal surface flat in its' distal half 

 and subobliquely deflexed. Eyes black, nearly linear, and trans- 

 verse. Antennules short, four-jointed, the basal joint but mode- 

 rately dilated. Antennae not exceeding one third the length of 

 the animal ; peduncle five-jointed, the first joint very short, the 

 fourth and fifth subequal ; flagellum with five or six distinct joints, 

 of which the first is very short, the second longest (apparently 

 composed of two coalescent joints), the rest short, tlie last beiag 

 minute and concealed by a pencil of short stiff hairs. Legs 



