Pallasea 



375 



extent beyond the others, inner ramus the shorter, but often nearly equal 

 to the outer. Telson seldom deeply cleft. 



10 species. 



Synopsis of species: 



t Antenna 1, accessory flagellum 1-jointed .... 1. P. dybowskii . . . p. 375 

 1 } Antenna 1, accessory flagellum with more than one 

 I Joint — 2. 



J Head with subdorsal dentate ridges 2. P. reissnerii . . . p. 376 



\ Head without dentate ridges — 3. 



/ Peraeon segment 5 distinguished by its large pair of 

 o J subdorsal teeth — 4. 



1 Peraeon segment 5 not distinguished by subdorsal 

 teeth — 5. 



( Teeth of peraeon segment 5 simple, bent backward 



4 l and downward 3. P. cancellus . . . p. 376 



I Teeth of peraeon segment 5 uhcinate,raisedupward 4. P. gerstfeldtii . . . p. 377 



j Subdorsal processes wanting on peraeon — 6. 

 \ Subdorsal processes present on peraeon — 8. 



j Uropod 3, inner ramus less than half outer . . 5. P. quadrispinosa . ji. 377 

 I Uropod 3, inner ramus more than half outer — 7. 



( Peraeon segments with median tubercles .... 6. P. kesslerii . . . . p. 378 

 \ Peraeon segments without median tubercles . . 7. P. baikali p. 378 



j Pleon segments with subdorsal and marginal 



8 ' processes 8. P. brandtii . . . . p. 379 



l Pleon segments without marginal processes — 9. 



I Peraeon segments 1 — 4 with paired tubercles in 



j median line 9. P. grubii p. 379 



\ Peraeon segments 1 — 4 with single (almost ob- 



' solete) tubercles in median line 10. P. cancelloides . . p. 380 



1. P. dybowskii Stebb. 1874 Gammarus asper (non J.D.Dana 1852!), B. 

 Dybowsky in: Horae Soc. ent. ßoss.. v. 10 suppl. p. 155 t. 13 f . 1 j 1893 Acanthonoto- 

 soma? a., A. DellaYalle in: F. Fl. Neapel, u 20 p. 927 | 1899 Pallasea dybowsUi, T. 

 Stebbing in: Tr. Linn. Soc. London, ser. 2 ?;. 7 p. 422. 



Peraeon segments 1 — 7 with lateral and marginal rows of tooth-like 

 carinae or tubercles, marginal much sbronger than the lateral, flattened, 

 the first 5 almost twice as long as last 2, 5*^ longer and more acute than the 

 preceding; lateral rows consisting of small tubercles, the first 5 the stronger, 

 the lateral rows slightly oblique. Pleon segments 1 — 3 with lateral rows of 

 small tubercles, obscurely continued on segments 4 — 6, on segments 1 and 2 

 a small median tubercle. Head with arched upper profile, rostral margin blunt, 

 little projecting; on the cheek-lobe a thick rounded hump prolonged outward 

 and downward. Side-plates 1 — 4 with no setae on lower margin, side-plate 4 

 with a central boss. Eyes not very large but very prominent, roundish, 

 brown. Antenna 1 about ^g as long as body, nearly twice as long as antenna 2, 

 peduncle somewhat longer than peduncle of antenna 2, flagellum 15 — 17-jointed, 

 accessory flagellum 1-jointed. Gnathopods 1 and 2, 6^*^ Joint larger in (S 

 than in 9 , in gnathopod 1 piriform, in gnathopod 2 oblong. Peraeopods 

 3 — 5, 2^ Joint moderately broad, elongate oval, with short, distant setae 

 on hind margin ; in peraeopod 5 wing produced downward in a rounded lobe. 

 Uropod 1 reaching end of peduncle of uropod 3. Uropod 2 reaching end of pleon 



