566 REV. T. E. R. STEBBING ON CRUSTACEANS [May 22, 



Trichoniscus magellanicus (Dana). 



1853. Styloniscus magellanicus, Dana, U.S. Expl. Exp. vol. xiii., 

 Crust, p. 736, pi. 48. figs. 7 a-g. 



1881. Styloniscus magellanicus, Miers, Pr. Zool. Soc. Lond. p. 77. 



1885. Styloniscus magellanicus, Budde-Lund, Crust. Isop. Ter- 

 restria, p. 271. 



Body smooth, narrowly elliptical ; front angles of first peraeon- 

 seginent rounded, not greatly produced, hind angles of this and 

 next segment rounded, of third subquadrate, of the rest successively 

 a little more and more produced backwards and sharpened, but in 

 none absolutely acute ; first the longest, rather longer than the head, 

 the others having the side-plates marked by a faint, obliquely 

 sinuous suture. Pleon abruptly narrower than peraeon, second 

 segment very short. Telson with sides converging from insertion 

 of uropods almost straight to broadly truncate apex. 



Eyes dark, with three visual elements. First antennae with 

 second joint shorter than first or third. Second antenna? spinulose, 

 with joints of peduncle successively longer, the last a little shorter 

 than the 7-10-jointed flagellum (7-8-jointed in specimens ex- 

 amined), last joint tipped with fascicle of seta?. 



Upper lip apically rounded and furred. Mandibles with toothed 

 cutting-edge narrow ; a single seta on right mandible ; molar cylin- 

 dric, prominent. First maxilla? : inner plate with three plumose 

 seta?, the inner the longest ; outer plate strap-shaped, surmounted 

 by eight unequal spines. Maxillipeds as partially figured by Dana, 

 and in near agreement with those of T.pusillus as figured by Sars, 

 but the epipod longer and distally furred with closely-set, very 

 short setules or spinules. 



Hind trunk-legs longer than those in front, all very similar in 

 structure ; the fifth joint carrying the strongest and longest spines ; 

 the sixth fringed on the outer margin with transparent spinules, 

 with little spines at intervals, also on the inner and part of the apical 

 margin showing, especially in the hinder pairs, thin membranous 

 expansions, as well as several spines ; the small seventh joint is 

 beset with various setules, among them along one with split apex, 

 and others with smoothly widened extremity (compare Chilton on 

 Philygria, 1886). In the second pleopods of the male the long 

 distal joint of the inner ramus is, till near the end, much more 

 widened than the stiliform joint figured by Sars for this part of 

 T. pygmaus. The uropods are as Dana figures them, the inner 

 ramus fully two-thirds as long as the outer, though in his description 

 he says " longer branch nearly twice the length of the other." 



Colour brown, mottled with yellowish white, especially a series 

 of light patches just above the side-plates of the peraeon. Length 

 about a third of an inch, or 8 mm. 



Mr. Vallentin's specimens were " found in a damp cave on the 

 top of a hill 450 feet high. 2 miles distant from Stanley." 



