Pallasea 377 



pointing blunt teeth, successively increasing towards and decreasing from 

 those of Segment 5, which are bent slightly backwärd and downward, and, 

 besides being stronger than the rest, are set nearer to the middle of the 

 back. In pleon segments 1 — 3 the lateral teeth are acute and rather long, 

 on Segments 4 and 5 they form weak carinae occupying about ^s length 

 of Segment. Head, upper surface smooth, rostrum minute, a flat subacute 

 tooth projecting outward on the under margin of the lateral lobes. Eyes 

 reniform or half-moon-shaped, black. Antenna 1 longer than half the body, 

 twice as long as antenna 2, 1^* Joint rather long, 3*^ shorter than 2*^, 

 flagellum 36 — 67-jointed, accessory flagellum 4 — 6-jointed. Antenna 2, 

 flagellum 8 — 14-jointed. Maxillipeds normal (Bäte: having a small squami- 

 form plate to the ischium only, but his figure shows 2*^ Joint produced as 

 well as the 3'^). Gnathopod 1, 6*'* Joint slender, piriform. Gnathopod 2, 

 6*^*^ Joint more rhomboidal, broader, palm oblique. Peraeopods 3 — 5, 2*^ Joint 

 heart-shaped, with short setae on the hind margin. Uropod 3, rami sub- 

 equal. Telson cleft \'., of length, each apex armed with a spinule. Colour 

 greenish-brown, or brown with scattered dots. L. ö attaining 70 mm to 

 eud of telson (with antenna 1:108 mm). 



Lake Baikal, near the shore; River Angara. 



4. P. gerstfeldtii (Dyb.) 1874 Gammanis canceUus var. g., ß. Dybowsky in: 

 Horae Soc. ent. E,oss., v. 10 suppl. p. 129 t. 2 f. 1 | 1893 Pallasea c. (part.), A. Della Valle 

 in: F. FI. Neapel, v.20 p.928 j 1899 P. gerstfeldtii, T. Stebbing in: Tr. Linn. Soc. London, 

 ser. 2 V.7 p. 422. 



Resembling P. cancellus, but very strongly developed. On peraeon 

 Segments 1 — 4 a median carina of strong blunt teeth, the edge of which is 

 often divided in segments 1 and 4; on segment 5 the carina is reduced to 

 a little point, on segments 6 and 7 it is broad-based, spine-like, but variable 

 in its strength and acuteness. The lateral teeth on peraeon segments 1 — 4 

 acute, successively longer, on segment 5 they are nearer to the median 

 line, and appear as reaching high over the body, gi'eatly curved or actually 

 uncinate and backward bent, the distance between their tips being twice the 

 breadth of the body at the base of the preceding pair of teeth; on segments 

 6 and 7 the lateral teeth are sharp; on pleon segments 1 — 3 they are 

 somewhat more bent, successively shorter, and on segments 4 and 5 they 

 are simple carinae. At the base of the lateral teeth, or between the latter 

 and the median teeth, there is a small tubercle on peraeon segments 6 and 7 

 and pleon segments 1 — 3. As in P. cancellus, there are tubercles and 

 spinules on the pleon segments 4 and 5, or 4^ — 6, the position of which is 

 not very clear. Head, the tooth on the under margin of lateral lobes is 

 more pointed and somewhat longer than in P. cancellus. Antenna 1, 3^ Joint 

 as long as 2*^, or somewhat longer. L. attaining 75 mm to end of telson. 



Lake Baikal. Depth 20—50 m. 



5. P. quadrispinosa 0. Sars 1861 Gammarus cancelloides (err., non Gerstfeldt 

 1858!), S. Loven in: Öfv. Ak. Förh., u 18 p. 287 | 1867 Pallasea c. var. qvadrispinosa, 

 G. O. Sars, Crust. d'Eau douce Norvege, p.68 t.6 f. 21- -34 ! 1876 P. q.. A. Boeck, Skand. 

 Arkt. Amphip., v.2 j). 375 j 1871 PaUasia q., A. Boeck in: Forh. Selsk. Christian., 1870 

 p.207 I 1894 P^llasiella q., O. 0. Sars, Crust. Norway, v.l p.506 t. 178 | 1874 Gammarus 

 kesslerii var. europaeus, B. Dybowsky in: Horae Soc. ent. Koss., nlO suppl. p. 135 | 1893 

 Pallasea caticellus (part.), A. Della Valle in: F. Fl. Neapel, f. 20 p. 755. 



Median carina wanting, body slender, peraeon segments 1 — 7 each 

 with supramarginal obtuse nodiform prominence; pleon segments 1 and 2 

 each with a pair of strong, subdorsal, backward directed, parallel teeth, wide 



