| OCR Text |
Show 566 REV. T. R. R. STEBBING ON CRUSTACEANS [May 22, TRICHONISCUS MAGELLANICUS (Dana). 1853. Stgloniscus magellanicus, Dana, U.S. Expl. Exp. vol. xiii., Crust, p. 736, pi. 48. figs. 7 a-g. 1881. Stgloniscus magellanicus, Miers, Pr. Zool. Soc. Lond. p. 77. 1885. Stgloniscus magellanicus, Budde-Lund, Crust. Isop. Ter-restria, p. 271. Body smooth, narrowly elliptical ; front angles of first peraeon-segment 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 antennae spinulose, with joints of peduncle successively longer, the last a little shorter than the 7-10-jointed flagellum (7-8-jointed in specimens examined), last joint tipped with fascicle of setae. Upper lip apically rounded and furred. Mandibles with toothed cutting-edge narrow ; a single seta on right mandible ; molar cylin-dric, prominent. First maxillae: inner plate with three plumose setae, 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 tbe 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; tbe small seventh joint is beset with various setules, among them a long 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. pygmceus. The uropods are as Daua 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 m m. Mr. Vallentin's specimens were " found in a damp cave on the top of a hill 450 feet high, 2 miles distant from Stanley." |
