518 Tritaeta, Paradexamine 



1893, 94 & 95 T. g., G. 0. Sars, Orust. Norway, v. 1 t. 168 f. 2; p. 479; p. 698 t. vm f. 1 | 

 1895 T. g., A. O. Walker in: P. Livei-p. biol. Soc, v. 9 p. 306 | 1881 Dexamine dolichonyx, 

 Nebeski in: Arb. Inst. Wien, v.S p. 145 t. 13 f. 40 | 1888 Tritaeta d., T. Stebbing in: Kep. 

 Voy. Challenger, v. 29 p. 520, 941, 945. 



Pleon Segments 1 — 3 in ö slightly raised dorsally. Side-plates 1 and 2 

 subquadrate, 3'^ and 4**^ acutely produced at the lower corners, 5*'^ with front 

 lobe the deeper, rouuded. Pleon segment 3, postero-lateral corners acute, 

 not greatly produced. Eyes large, rounded oval, larger in d, reddish brown 

 with whitish coating. Antenna 1 long, 1^* Joint much shorter than 2*^, 

 flagellum twice as long as peduncle, about 18-jointed. Antenna 2 in g 

 scarcely so long, ultimate Joint of peduncle shorter than penultimate, flagellum 

 about 18-jointed; in c5' longer than antenna 1, penultimate and antepenultimate 

 joints of peduncle densely fringed above, flagellum about 24-jointed. Gnatho- 

 pod 1, 5*^1 Joint distally widened, rather shorter than 6*'\ which is a short 

 oval, widening to the palm ; palm slightly oblique, fairly well defined. Guatho- 

 pod 2 longer, 5*^ Joint slender, little widened distally, quite as long as 6*^, 

 which is longer and more slender than in gnathopod 1. Gnathopod 1 often 

 has a deep sinus in the front margin of the 6^^ Joint in ö and at least 

 occasionally also in Q , perhaps a copulatory feature. Peraeopods 1 — 5, 

 4*^ Joint longer than 5*^ and 6*^ combined, 5*^ armed with 5 sti'ong spines 

 on expanded extremity; 6*^' rather longer in peraeopods 1 and 2, equal or 

 shorter in 3*^ — 5^\ in all facing backward, not expanded distally; finger strong 

 and curved. Peraeopod 3, 2^ Joint narrowly oblong oval, in peraeopod 4 

 narrower, with angular projection proximally, in peraeopod 5 sublinear, slightly 

 widened proximally. Branchial vesicles simple in 9, pleated in d. Üropod 3, 

 rami scarcely twice as long as peduncle, narrowly lanceolate, spinöse. Telson 

 rather over twice as long as broad, cleft nearly to base, in o with 3 marginal 

 and 3 submarginal spines on each side, and 1 spine on each obtuse apex, 

 in d with an additional marginal spine (Sars). Colour dark brownish with 

 opaque white patches. L. 6 mm. 



North- Atlantic and North-Sea (Norway, France, British Isles, Azores); Mediterranean. 



3. Gen. Paradexamine Stebb. 



1899 Paradexamine (Sp. typ.: Dexamine pacifica), T. Stebbing in: Ann. nat. Hist., 

 ser, 7 u 4 p. 210. 



In general character like Dexamine (p. 514), but distinguished as follows. 

 Lower lip with inner lobes well developed and mandibular processes upturned. 

 Maxilla 1 with the 1-jointed palp uniform in left and right maxilla. Maxillipeds 

 with smal] distinct finger to the palp. 



1 species. 



1. P. pacifica (G. M. Thoms.) 1879 Dexamine p., U. M. Thomson in: Tr. N. 

 Zealand Inst., v.U p. 238 t. 10b f. 4 | 1886 D. p., G.M.Thomson & Chilton in: Tr. 

 N. Zealand Inst., v. 18 p. 149 | 1899 D. p., Paradexamine sj). typ., T. Stebbing in: Ann. 

 nat. Hist., ser. 7 v.A p. 210 | 1893 D. spinosa (part.), A. Della Valle in: F. Fl. Neapel, 

 V. 20 p. 574. 



Peraeon and pleon segment 1 dorsally rounded, pleon segments 2 — 4 

 carinate, segment 1 sometimes produced to a dorsal tooth or 3 teeth, segments 2 

 and 3 produced to 3 large dorsal teeth, largest in segment 3, segment 4 

 produced into a large tooth slightly upturned at the acute apex, a dorsal 



