576 Hyalella 



produced a little bejond front, though uot enougli to form a proper chela 

 between the small palm and small finger. Peraeopods 3 — 5, 2^ Joint broad, 

 serrate, but smooth in Saussure's figure, Peraeopod 5 little longer than 

 peraeopod 4. üropod 3, ramus nearly as long as peduncle, sleuder, tapering, 

 with setae at apex. Telson stout, as long as broad; apical margin rounded, 

 lyith slender seta on each side. L. about 4 — 6 mm. 



Mexico; North America (Florida, Connecticut etc.). Streams, lakes, stagnant water. 



2. H. echinus (Faxon) 1876 Ällorchestes e., Faxon in: Bull. Mus. Harvard, v.B 

 p.367 f. 19— 21 I 1888 Hyalella e., T. Stebbing in: Rep. Voy. Ghalienger, r. 29 p.455| 

 1893 H. e., A. Della Valle in: F. Fl. Neapel, u20 p. 517 t. 58 f. 12, 13. 



Body Short, very stout, peraeon segments 1 — 7 and pleon segments 1 — 4 

 «ach having on bind margin 2 medio-dorsally elevated spine-like processes, 

 and peraeon segments 1 — 7 with pleon segment 1 each having a small 

 marginal process on either side. Head with small deflexed rostral point, 

 a tubercle on each cheek. Side-plates 1 — 4 large, ti'iangular, with ridge 

 from centre of base to apex. Side-plate 4 with tubercle on bind margin, 

 side-plate 5 with tubercle on each lobe. Eyes round, large, protuberant. 

 Antenna 1, flagellura 6 — 8-jointed. Antenna 2, flagellum 9-jointed. Gnatho- 

 pod 2 in ö, 6*'^ Joint large, somewhat widened to the rather oblique, slightly 

 concave palm, which receives point of finger in a terminal uotch. Gnatho- 

 pod 2 in 9 , 5*^ and 6*^ joints subequal. Peraeopods 3 — 5, 2*^ Joint moderately 

 expanded; peraeopod 3 only -/s as long as the elongate, subequal 4*^ and 

 5*^ peraeopods. L. 5 — 7 mm. 



Lake Titicaca. Depth 18 — 110 m. 



3. H. longipes (Faxon) 1876 Allorchestes l, Faxon in: Bull. Mus. Harvard, 

 «.3 p.368 f. 22— 25 | 1888 Hyalella l, T. Stebbing in: Rep. Voy. Challenger, u29 p.455 j 

 1893 H. l, A. Della Valle in: F. Fl. Neapel, v. 20 p. 515 t. 58 f. 6, 7. 



Peraeon segment 1 with front margin forming a short medio-dorsal 

 tooth; peraeon segments 1 — 7 and pleon segments 1 — 3 each with bind margin 

 produced to a backward-pointing, medio-dorsal tooth or spine-like process, 

 small on peraeon segments 1 — 4 (the first 2 teeth sometimes longer, curved 

 f orward), large on the others, largest on pleon segments 1 and 2 ; pleon seg- 

 ment 4 with bind margin forming a median projection either subacute or 

 convex. Side-plates 1 — 4 long, apically pointed. Pleon segments 1 — 3, 

 postero-lateral corners slightly produced. Eyes round, protuberant. Antenna 1, 

 flagellum 13-jointed. Antenna 2 somewhat longer, flagellum 14-jointed. 

 Gnathopod 2 in 05", 6*^ Joint not very large, widening to palm, which is not 

 very oblique, detined by a small projecting tooth. Peraeopods 4 and 5 very 

 long, üropod 3 very short, with a very slender seta at tip. L. about 10 mm. 



Lake Titicaca. Depth 20—72 m. 



4. H. lucifugax (Faxon) 1876 Allorchestes l., Faxon in: Bull. Mus. Harvard, 

 ».3 p. 369 f. 26 I 1888 Hyalella l, T. Stebbing in: Rep. Voy. Challenger, u 29 p.455 | 

 1893 H. l, A. Della Valle in: F. Fl. Neapel, v. 20 p. 515 t. 58 f. 4, 5. 



9 unknown. — ö . Very like H. longipes, with the same number of dorsal 

 processes, but 1^* dorsal tooth overlies the head, the next 6 are also large, 

 curved forward. Side-plates 1 — 4 with rounded apices. Antennae 1 and 2 

 subequal. L. 11 mm. 



Lake Titicaca. Depth 72—110 m. 



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