376 Fallasea 



Segment 6, which is twice as long as segment 5. Uropod 3 in ö V?» in 

 9 ^9 äs long as body, rami subequal, fringed with plumose setae. Telson 

 much shorter than peduncle of uropod 3, rounded pentagona!, apical border 

 almost ti'uncate or faintly concave. Colour dark grey brown, with brighter 

 markings and stripes, a dark stripe along the back, carinae darker than the 

 rest of the body, often those to the rear red. L. 17 mm. 



Lake Baikal. Depth 10 m. 



2. P. reissnerii (Dyb.) 1874 Gammarus r., B. Dybowsky in: Horae Soc. ent. 

 Ross., V. 10 suppl. p. 126 t. 3 f. 1; t. 4 f. 7 1 1893 Paüasea? reissneri, A. DellaValle in: 

 F. Fl. Neapel, i;.20 p. 930 ] 1899 P. reistierii, T. Stebbing in: Tr. Linn. Soc. London, 

 ser. 2 V. 7 p. 422. 



Peraeon segments 1 — 3 with 2 rather remote median tubercular carinae, 

 which dwindle away on segments 4 and 5, and are replaced by a single 

 carina on segment 6, which gradually encreases in height to pleon segment 3, 

 successively more clearly divided by a saddle-shaped Depression of the upper 

 margin into 2 halves, of which the hinder is tooth-like, and on pleon 

 segment 3 bent forward as a hook; pleon segment 4 with a tubercular 

 keel, segments 5 and 6 quite flat. Peraeon segments 1 — 7 have marginal 

 keels, perhaps representing a coalescence of marginal with subdorsal processes, 

 the processes on segments 1 — -5 tolerably long and acute, on segments 

 6 and 7 blunt, tubercular. The swellings on the pleon segments are feebly 

 indicated. Head, rostral point insignificant, upper surface rough, separated 

 from the sides by ridges which have tolerably high, flat teeth at the ends; 

 there is a lateral swelling above the eyes, and below and somewhat behind 

 them a flat, double-pointed process. Eyes small, irregularly reniform, white. 

 Antenna 1 half as long as body, about Yg longer than antenna 2, 1^^ Joint 

 thick, longer than 2^ and 3<^ cömbined, flagellum 32-jointed, accessory flagellura 

 3-jointed. Antenna 2, ultimate and penultimate joints of peduncle equal, 

 flagellum 12-jointed. Gnathopod 1, 6**^ Joint slender, piriform, finger short. 

 Gnathopod 2, ö*** Joint longer than in gnathopod 1, 6'*^ Joint slender, oblong, 

 palm rather oblique, finger short. Peraeopods 3 and 4, 2^ Joint more or 

 less heart-shaped. Peraeopod 5, 2^ Joint oblong, with rather long setae on 

 bind margin, as in peraeopods 3 and 4. Uropod 3, outer ramus about ^5 

 longer (not shorter, as misprinted in Dybowsky, p. 126) than the inner, 

 2^ Joint scarcely perceptible. Telson divided beyond the middle, with blunt 

 apices (in flgure). Colour white with shimmer of brown. L. (S 25 mm. 



Lake Baikal. Depth 1300 m. 



3. P. caneellus (Fall.) 1772 Oniscus c. (Cancer baikalensis Laxraan in 3IS.), 

 Pallas, Spie, zool., t;.9 p. 52 t. 3 f. 18 1781 Gammarus c, J. C. Fabricius, Spec. Ins., 

 V. 1 p. 515 I 1874 G. c, B. Dybowsky in: Horae Soc. ent. ßoss., v.lO suppl. p. 127 | 1798 

 Cancer (Gammardlus) c, J. F. W. Herbst, Naturg. Krabben Krebse, ».2 p. 125 t. 35 f. 12 | 

 1806 C. (Gammarus) c, Turton in: J. F. Gmelin, Gen. Syst. Nat.. u.S p. 760 i 1825 

 Amphithoe c, A. G. Desmarest, Consid. gen. Crust., p. 268 | 1830 A. cnncella, H. Milne 

 Edwards in: Ann. Sei. nat., v.20 p. 377 ] 1862 Pallasea caneellus (Gammarus latreillii 

 Guerin-Meneville in MS.), Bäte, Cat. Amphip. Brit. Mus., p. 200 t. 36 f. 1 | 1893 P. c. 

 (part.), A. DellaValle in: F. Fl. Neapel, v. 20 p.755 t. 60 f. 26, 27 | 1776 Oniscus mtiricatus, 

 Pallas, Reise Ruß., v.3 p. 709. 



Peraeon segments 1 — 7 and pleon segments 1 — 4 with a weak median 

 carina formed by a small tubercle or blunt hump, the humps being sti'ongest 

 on the pleon segments. Iramediately above the side-plates the margins of 

 the peraeon segments form a weak carina, close above which are backward 



