Pseudalibrotus 33 



19. Gen. Pseudalibrotus Della Valle 



1871 Onisimus (part.), A. Boeck in: Forh. Selsk. Christian., 1870 p. 112 | 1876 

 Onesimus (part.), A. Boeck, Skand. Arkt. Amphip., v. 2 p. 161 | 1893 Pseudalibrotus 

 (Sp. un.: P.littoralis) (part), A. Della Valle in: F. Fl. Neapel, u 20 p. 798 i 1896 P., 

 G. 0. Sars in: Bull. Ac. St.-Petersb., ser. 5 vA p. 422. 



Body rather slender and compressed. Side-plates not very large, 4^^ 

 pair deeply but narrowly emarginate behind. Antenua 1 and 2, with many 

 Short joints in the flagella both of d and g . Epistome not distinctly 

 defined from upper lip, both together forming a rounded prominence. Lower 

 lip with front lobes a little emarginate distally. Mandible, molar rather 

 strong, palp large, set well forward. Maxilla 1, inner plate small with 

 2 setae, outer plate broad, obliquely truncate, palp with small apical teeth. 

 Maxilla 2, inner plate much shorter than outer. Maxillipeds normal, outer 

 plates crenulate, not reaching end of 2^ Joint of palp, 1^* — 3*^ joints of palp 

 robust, 4*^ small, unguiform. Gnathopod 1 subchelate, 6*^ Joint a little 

 longer than 5*^, oblong, palm oblique, 7**1 Joint simple. Gnathopod 2, 6*^ 

 Joint about half length of o*^ slender, oblong, more or less produced, sub- 

 chelate or chelate. Peraeopods 3 — 5, 2*^ Joint large, longer than broad. 

 Uropod 3, rami longer than peduncle, outer rather the longer. Telson 

 Short, broad, entire. 



3 species. 



Synopsis of species : 



j Gnathopod 1 very robust 1. P. litoralis • . . p. 33 



) Gnathopod 1 not very robust — 2. 



( Pleon Segment 3, postero-lateral corners considerably 



) produced 2. P. caspius . . . p. 34 



I Pleon segment 3 , postero - lateral corners scarcely 



' produced 3. P. platyeeras . p. 34 



1. P. litoralis (Kreyer) 1845 Änonyx l., Kreyer in: Naturh. Tidsskr., ser. 2 

 v.l p. 621 i 1846 A. littoralis, Xreyer in: Voy. Nord, Crust. 1. 13 f. la-t j 1862 Alibrotus l, 

 Bäte, Cat. Amphip. Brit. Mus., p. 86 t. 14 f. 7 i 1891 .4. /., G. 0. Sars, Crust. Norway, 

 v.l p. 102 t. 35 f. 2 I 1894 A. litoralis, T. Stebbing in: Bijdr. Dierk., u 17 p. 9 | 1866 

 Lysianassa l., Goes in: Öfv. Ak. Förh., r. 22 p. 521 | 1871 Onisimus l., A. Boeck in: 

 Forh. Selsk. Christian., 1870 p. 112 | 1875 0. l, Cam. Heller in: Denk. Ak. Wien, v. 35 

 p. 31 t. 2 1.8—16 I 1876 Onesimus l, A. Boeck, Skand. Arkt. Amphip., v.2 p. 162 t. 5 

 f. 7 ! 1893 Pseudalibrotus littoralis (part.), A. Della Valle in: F. Fl. Neapel, «.20 p. 799. 



Head, lateral lobes narrowly rounded, little prominent. Side- plate 1 

 much expanded distally. Pleon segment 3, postero-lateral angles minutely 

 outdrawn, almoät quadrate. Eyes small, rounded oval, red. Antenna 1, 

 1^* Joint more than twice as long as 2*^ and 3*1 combined, flagellum in Q with 

 26 joints, 1^* much the largest, accessory flagellum with 5 joints, 1^* as long 

 as the rest combined. Antenna 2, ultimate Joint of pednncle shorter than pen- 

 ultimate, flagellum in 9 about 30-jointed. Flagella in ö rather longer than 

 in 9 and with müiny more joints. Gnathopod 1 strong, 5^^ Joint distally broad, 

 6*^ broadly oblong, palm spinulose, with 2 spines at the angle. Gnathopod 2, pahn 

 minutely produced. Peraeopods 1 and 2, 6^^ Joint slightly curved. Peraeo- 

 pods 3 — 5, 5^^ and 6*^ joints slender. üropod 2, inner ramus constricted. 

 üropod 3, outer ramus with small 2*^ Joint and setose on inner margin. 

 Telson rounded, scarcely longer than broad, distal border faintly emarginate 

 in the centre, carrying two spinules. Colour whitish. L. 13 — 18 mm. 



Arctic Ocean (North-Norway). 



Das Tierreich. 21. Lief.: T. R. R. Stebbing, Amphipoda I. 3 



