Dexamine 515 



Lower lip with rudimentaiy inner lobes. Mandible, spine-row veiy small. 

 Maxilla 1, inner plate with 1 seta, outer with 11 spines, palp's singie joiut 

 rathcr large, apically smooth on one maxilla, denticulate on the other. Maxilla 2 

 rather small, armed only at the apices. Maxillipeds, inner plates rather small 

 but well developed, outer plates almost covering the slender 3-jointed palp, 

 fringed with spine-teeth on inner margin. Gnathopod 2 rather longer than 1®*. 

 Peraeopods 3 — 5, 2^ joiut successively less expanded. Uropod 3, rami naiTowly 

 lanceolate. 



4 species accepted, 4 doubtful. 



M 



Synopsis of accepted species: 



Pleon Segment 3 dorsally unidentate — 2. ' . 



Pleon Segment 3 dorsally tridentate — 3. 



Peraeopod 5, 2<1 Joint laminar I.D. spinosa p. 515 



Peraeopod 5, 2d Joint sublinear 2. D. thea p. 516 



j Pleon Segment 2 tricarinate 3. D. spiniventris . . . p. 516 



\ Pleon segment 2 not tricarinate 4. D. blossevilliana . . p. 517 



1. D. spinosa (Mont.) 1813 Cancer (Gammarus) spinosus, Montagu in: Tr. 

 Linn. Soc. London, v. 11 p. 3 t. 2 f. 1 | 1818 6r. s., Lamarck, Hist. An. s. Vert., v. 5 

 p. 181 I 1813/14 Dexamine spinosa, Leach in: Edinb. Enc, v.7 p. 432 | 1862 D.s., 

 Bäte & Westwood, Brit. sess. Crust., v. 1 p. 237 f. j 1862 D. s., Bäte, Cat. Amphip. 

 Brit. Mus., p. 130 t. 24 f. 1 | 1876 D. s., A. Boeck, Skand. Arkt. Amphip., v. 2 p. 312 

 t. 11 f. 5 I 1893 D. s. (part.), A. Della Valle in: F. Fl. Neapel, v.20 p. 573 t. 5, 12; 1. 18 

 f. 1—17, 19 I 1893 & 94 D. s., G. 0. Sars, Crust. Norway, v. 1 t. 16b f. 2; 1. 167; p. 475 | 

 1840 Acanthonotus? s., H. Milne Edwards, Hist. nat. Crust., v.S p.25 | 1855 Ämphithoe s., 

 Gosse, Man. mar. Zool., v.l p. 141 f. 266 | ?1826 Atylus cwallinus, A. Risso, Hist. nat. 

 Eur. merid., v.5 p. 99 | 1830 ÄniphitJwe mariotiis, H. Milne Edwards in: Ann. Sei. 

 nat., t). 20 p. 375 | 1857 Amphithonotus m., A. Costa in: Mem. Acc. Napoli, v. 1 p. 195 | 

 1843 Ämphithoe tenuicornis, H. Rathke in: N. Acta Ac. Leop., v.20i p. 77 t. 4 f . 3 ' 

 1859 Gammarus speciosus (laps., corr. : G. spinosus) -\- Dexamine t., R. M. Bruzelius in: 

 Svenska Ak. Handl., n. ser. v. 3 nr. 1 p. 79 | 1851 Amphithonotus acanthophthalmus, 

 (A. Costa in:) F.W. Hope, Cat. Crost. Ital., p.45 1 1868 Dexamine spiniventris var. pontica, 

 Czerniavski in: Syezda Russ. Est., Syezda 1 Zool. p. 111 t. 8 f. 16 | 1898 D. spinosa 

 var.?, Sowinski in: Mem. Soc. Kiew, v. 15 p. 490 t. 12 f. 5, 6. 



Peraeon robust, pleon cariuate, segments 1 — 4 each produced to a 

 strong dorsal tooth, hinder part of segments 5 and 6 with 3 small dorsal 

 ridges each ending in a small tooth. Head, rostrum short, blunt at apex, 

 lateral corners triangulär, acute. Side-plate 1 a little concave in front, 

 4*^^ deeper than the rest. Pleon segment 3, postero-lateral corners sharply 

 produced. Eyes oblong- reniform, larger in ö than in Q , dark brown with 

 whitish coating. Antenna 1, 1^* Joint produced to an obtuse tooth (or acute, 

 Sowinski), 2*^ much narrower and over once and- a half as long, 3*^ very 

 Short (or not very short, Sowinski), flagellum about twice as long as peduncle, 

 30 — 45-jointed. Antenna 2 in Q shorter, in ö longer than antenna 1, 

 ultimate Joint of peduncle longer than penultimate, flagellum filiform. 

 Gnathopod 1, 2^ Joint curved, 5*^ shorter than 6*^, widened distally, 6*^^ expauding 

 to the palm which is oblique, as long as hind margin, well defined by the 

 palmar spines at the obtuse angied junction. Gnathopod 2, 2"^ Joint longer, 

 curved, 5*^ little widened distally, as long as 6*^, which is similar to that 

 of gnathopod 1 but longer. Peraeopods 1 and 2 alike, 6^^ Joint longer 

 than 5*^, finger rather strong. Peraeopods 3 — 5, 6**^ Joint shorter than 5*^. 

 Peraeopod 3, 2"^ Joint oblong oval, lower hind corner produced in a rounded 



83* 



