374 Hyalellopsis, Pallasea 



6. Gen. Hyalellopsis Stebb. 



1899 Hyalellopsis (Sp. typ. : H. czyrnia^skii), T. Stebbing in : Tr. Liun. Soc. London, 

 ser. 2 t;. 7 p. 422. 



Body (Fig. 85) smooth, pleou segments 4 — 6 very short. Head, rostruni 

 insignificant. Side-plates 1 — 4 moderately deep, rounded below, setuliferous, 

 4**^ excavate behind, much deeper than 5*^\ Antennae 1 and 2 short, antenna 1 

 ratlier the longer, with 1-jointed accessory flagellum. Mouth-parts perhaps as in 

 Gammarus (p. 460). Gnathopods 1 and 2 subchelate. Peraeopods 1 — 4, 2*^ Joint 

 lieai"t-shaped.- Peraeopod 5 short, 2'^ Joint as long as rest of limb, much 

 expanded and distally produced. üropods 1—3 short, especially uropod 3, 

 which is uniramous. Telson small, rounded. 



1 species. 



1. H. czyrnianskii (ßyb.) 1874 Gammarus c, B. Dybowsky in: Horae Soc. 

 ent. Eoss., u 10 suppl. p. 15B t. 9 f. 5 j 1899 HyaleUopsis c, T. Stebbing in: Tr. Linn. 

 Soc. London, ser. 2 «. 7 p. 422. 



Surface of body (Fig. 85) free from prominences, setae, spines, or hairs. 

 Head, lateral lobes truncate, little produced. Pleon segment 3, postero- 

 lateral corners (in ligure) rounded. Eyes small, roundish, very pi-ominent, black. 

 Antenna 1 about 7* as long as body, little longer than antenna 2, peduncle 

 stouter and somewhat longer, its 1^* Joint stout, flagellum 

 9 — 11-jointed, a little longer than peduncle; antenna 2, 

 flagellum 5 — 8-jointed. Gnathopod 1, 6*^ Joint piriform, 

 more slender in d than in 9 . Gnathopod 2, 6*^ Joint 

 oblong. Peraeopods 3 and 4, 2*^ Joint having the slightly 

 convex hind margin beset with short setae. Peraeopod 5, 

 2*^ Joint having hind margin evenly rounded, produced 

 below into a rounded lobe, and carrving short setae. 



Vis 8t ' . o 



H czyrniaiskii wMle the front margiu has long stout setae in fascicles. 



Lateral view. Üropods 1 and 2 are said to reach beyond uropod 3 



[After B. Dybowsky.] (scarccly iu figure). üropod 3 very short, rudimentarjr, 



ramus set like a stump on the short, broad peduncle, and 



carrying on its flat broad apex 5 or 6 stout spines. Telson small, leaf- 



like, semicircular. Colour dark horn-gi"ey. L. c? 11, O 7 mm. 



Lake Baikal. Depth 10 m. 



7. Gen. Pallasea Bäte 



1793 [Subgen.] Gammarellus (part.), J. F. W. Herbst, Xaturg. Krabben Krebse, 

 V. 2 p. 106 I 1862 Pallasea, Bäte, Cat. Amphip. Brit. Mus., p. 200 [ 1867 F., G. ü. Sars, 

 Crust. d'Eau douce Xorvege. p. 67 | 1876 E, A. Boeck. Skand. Arkt. Ampliip., r.2 

 p.374 I 1893 P., A.Della Valle in: F. Fl. Neapel, t;.20 p. 755 | 1899 F., T. Stebbing in: 

 Tr. Linn. Soc. London, ser. 2 v. 7 p. 422 | 1871 Fallasia (non Robineau-Desvoidy 1830, 

 Diptera!), A. Boeck in: Forb. Selsk. Christian., 1870 p.206 | 1894 Fallasiella, G. 0. Sars, 

 Crust. Norway, v. 1 p. 505. 



Kows of processes arming the back and sides or sides alone of some 

 of the Segments. Head, rostrum obsolete. Eyes prominent. Antenna 1 the 

 longer, peduncle long, accessory flagellum rather short. Mouth-parts normal. 

 Gnathopods ] aud 2 subchelate. Peraeopods 3 — 5 rather slender, 2^ Joint 

 not greatly expanded, most so in peraeopod 5. üropod 3 reaching to some 



