14 Trischizostoma, Acidostoma 



3*^ Joint very long, much more so in ä than 9; the 5*'^ longer in 9 than c?; 

 6*^1 oval, densely setose; 7**^ minute, inserted on the middle of distal margin 

 ol 6*^\ Peraeopods 1 and 2, 2*^ Joint a little dilated, seemingly more in 6 

 than in 9 ; 4*^ Joint dilated, especially in peraeopod 2, seemingly less in d 

 than in 9. Peraeopods 3, 4 and 5 rather short, successively longer; 2'^ Joint 

 laminar. Telson rounded, almost as broad as long; apex obtusely truncated in 9 , 

 broad, oval in cJ, with a small emargination in young (5 (Bovallius' figure). 

 Colour whitish with light reddish tinge on sides (Sars), white as ivory; the 

 eyes dark brown (Costa and Bovallius). L. 9 22 — 30, ö 12 — 13 mm. 



North-Sea, Skagerrak, North-Ätlantic and Arctic Ocean (South-, West- and North- 

 Norway), depth 190 — 475 m; Mediterranean. Usually on fishes. 



3. Gen. Acidostoma Lillj. 



1865 Acidostoma (Sp. un.: A. obesutn), W. Lilljeborg in: N. Acta Soc. Upsal., 

 ser. 3 V.6 nr. 1 p. 18, 34 | 1890 A., G. O. Sars, Crust. Norway, v. 1 p. 37. 



Body Short, robust. Side-plates large, deep. Antenna 1, 2^ and 3'^ joints 

 Short, in ö but not in 9 nearly as stout as the 1^*; P* Joint of flagellum 

 small in 9 , in d laminar, densely fringed ; accessory flagellum in ö and 9 

 nearly as long as primary. Antenna 2 rather slender. Upper lip long, narrow. 

 Lower lip with the lobes narrowed. Mandible with minute tooth at each 

 end of cutting edge, narrow, simple; no molar; palp slender, nearly as long 

 as the trunk, armed only at apex. Maxiila 1, inner plate small, narrow; outer 

 plate narrow, tipped with small unguiform teeth, palp a rudiment. Maxilla 2, 

 both plates stiliform. Maxillipeds, inner plates tapering, outer large without 

 marginal teeth, palp scarcely reaching beyond outer plate, its 4*^ Joint rudi- 

 mentary. Gnathopod 1 rather robust, 5^^ Joint subequal in length to 6*^, 

 the latter tapering, without palm. Gnathopod 2, 6*'^ Joint uarrowly oblong, 

 densely hirsute, 7^^ wanting. Peraeopods 3, 4 and 5 robust, 2*^ and 4**» joints 

 much expanded. üropod 2 with broad peduncle; uropod 3 very small. 

 Telson short, broad, more or less cleft or emarginate. 



2 species. 



Synopsis of species: 



Telson rather deeply cleft I.A. obesum . . . p. 14 



Telson slightly emarginate 2. A. laticorne . . p. 14 



1. A. obesum (Bäte) 1862 Anonyx obesus, Bäte, Cat. Amphip. Brit. Mus., p. 74 

 t. 12 f . 1 I 1865 Acidostoma obesum, W. Lilljeborg in: N. Acta Soc. Upsal., ser. 3 v.ß 

 nr. 1 p. 34 t. 5 I 1890 A. 0., G. 0. Sars, Crust. Norway, v. 1 p. 38 t. 14 f. 2. 



Pleon Segment 3 with postero-lateral angles narrowly rounded. Eyes 

 small, rounded, brownish. Antenna 1 in 9 , flagellum 7-jointed, accessory 

 flagellum 5-jointed, in ö 1^* Joint of flagellum large, flattened, but arched 

 below and armed with sensory filaments. üropod 3 scarcely half as long as 

 uropod 2, the rami lanceolate, unarmed, the outer one the longer. Telson 

 almost as broad as long, rounded, cleft beyond the middle. Colour pale 

 orange with light red bands across the segments. L. 5 mm. 



North- Atlantic, North-Sea and Skagerrak (Moray Firth, Shetland Islands, South- 

 and West-Norway, Bohuslän, South-West-England, West-France). Depth, low tide 

 mark to 90 m. 



2. A. laticorne 0. Sars 1879 A. laticornis, G. 0. Sars in: Arch. Naturv. 

 Kristian., t;. 4 p. 440 | 1885 & 86 A. laticorne, G. 0. Sars in: Norske Nordhavs-Exp., 

 Ü.6 Crust. I p. 152 t. 13 f. 3, 3 a (cJ) | ?1893. A. l, A. Della Valle in: F. Fl. Neapel, v. 20 

 p.782. 287, 769; t. 6 f. 12; t. 28 f. 1—21(9) I 1886 A. obesum (err., non Anonyx obesus 

 Bäte 1862!) + A l., G. 0. Sars in: Norske Nordhavs-Exp., v.6 Crust. II p. 43, 44. 



