Pleustidae, Pleustes 309 



23. Farn. Pleustidae 



1874 Subfani. Pleustinae, Buchholz in: Zweite D. Xordpolarf., t\2 p. 333 | 1888 

 Pleustidae, T. Stebbing in: Rep. Voy. Challenger, r. 29 p. 870 | 1893 Paraniphithoidae, 

 G. O. Sars, Crust. Norway, v. 1 p. 343. 



Rostrum more or less prominent. Side-plates 5 — 7 small. Antenna 1 

 without accessory flagellum, longer tiian antenna 2, flagellum in both many- 

 jointed. Cpper lip unsyrametrically bilobed. Lower lip, inner lobes continuous 

 with outer, little prominent. Mandible, accessory plate sometimes wanting 

 on rigbt, palp well developed, 3"^ Joint falciform. Maxilla 1, inner plate small, 

 with 1 — 4 setae. Maxillipeds, inner and outer plates ratber small, not 

 strongly armed, palp long. Gnatbopods 1 and 2 often alike, subcbelate. 

 Peraeopods 3 — 5, 2*^ Joint expanded. Braucbial vesicles ratber small, simple. 

 Uropod 3. rami longer than peduncle, slender, lanceolate, spinulose, outer 

 shorter tban inner. Telson small, entire or (very rarely) notched, boat- 

 shaped. Sexual difference very sligbt. 



Marine. 



5 aecepted genera and 1 doubtful, 18 accepted species and 4 doubtful. 



Synopsis of accepted genera: 



j Mandible, molar feebly developed — 2. 

 ) Mandible, molar strongly developed — 3. 



{Mandibular p^lp of moderate size; gnathopods 1 

 and 2 powerful 1. Gen. Pleustes. . . . p. 309 

 Mandibular palp large; gnathopods 1 and 2 of 

 moderate size 2. Gen. Neopleustes . . p. 311 



I Maxillipeds, finger of palp strong 3. Gen. Mesopleustes . p. 315 



\ Maxillipeds, finger of palp slight — 4. 



I Mandible, molar compressed; maxilla 1, inner 



I plate with 1 seta 4. Gen. Stenopleustes . p. 316 



I Mandible, molar cylindric; maxilla 1, inner 



' plate with 2 setae 5. Gen. Sympleustes . . j). 317 



1. Gen. Pleustes J3ate 



1858 Pleustes (Sp. un.: P. tuberculata), Bäte in: Ann. nat. Hist., ser. 3 v.l p. 362 

 1876 P. (part.), A. Boeck, Skand. Arkt. Amphip., v.2 p.299 | 1893 P., G. 0. Sars, Crust. 

 Norway, v.l p.343 | 1859 Paramphithoe (jpurt.), R. M. Bruzelius in: Svenska Ak. Handl., 

 n. ser. v.S nr. 1 p. 68 | 1871 P., A. Boeck in: Forh. Selsk. Christian., 1870 p. 174. 



Coating indurated, witb keels or tubercles. Rostrum large, flat. 

 Side-plates 1 — 4 large, 4*^ emarginate bebind. Antennae 1 and 2 not 

 elougate. Upper lip, lobes subequal, finely birsute. Mandible, molar feeble^ 

 palp of moderate size. Maxilla 1, inner plate witb 1 seta, outer with 

 9 spiues. Maxilla 2, inner plate the wider. Maxillipeds, outer plates scarcely 

 reaching beyond 1^* Joint of elongate palp. Gnathopods 1 and 2 powerful, 

 5* Joint Short, produced to a narrow lobe, 6*1' large, oval, palm oblique, 

 well defined, tufted with spines. Peraeopod 4 little longer than 3^ and 5^^^ 

 little longer tban 4*^. Telson broadly rounded at apex. 



2 species accepted, 3 obscure. 



