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Show 550 REV. T. R. R. STEBBING ON CRUSTACEANS [May 22, measured. The distinction of /. hargeri from /. pubescens is only effected by attributing to Dana's description and figures a minute accuracy to which they have no claim, and which at the date of their production was scarcely ever accorded to small crustaceans. Dana, for example, says " Caudal stylets half as long as abdomen, three- or four-jointed," though his fig. 9 d shows the stylets with single-jointed rami and only about one-fourth as long as the pleon. That Pfeffer's deer a antarctica may be an additional synonym is of necessity conjectural. The solitary specimen was imperfect and could not be dissected. The length is given as 3-2 mm., and the greatest breadth as not much more than one-fourth of tbe length; just as Bovallius says of Iais hargeri, " the body is elongate, linear, four times longer than broad." This, it is likely, refers to the male. In I. pubescens the female loses something of her slenderness of shape as the marsupium becomes inflated. On the other hand, Pfeffer definitely states that the finger is biunguiculate and that the 3-unguiculate finger, which he, like Sars, attributes to Jcera, was not to be found on any of the limbs of the peraeon. He also gives the colour as brownish, whereas the Falkland Island specimens better agree with Bovallius's account of /. hargeri, as " greenish white, almost hyaline." Pfeffer's description of the damaged first antennae and of the uropods tallies well with what is found in /. pubescens. Mr. G. M . Thomson found Tasmanian specimens of I. pubescens in a tube with " Sphceroma quoyana M.-Edw.," but it may be noticed that he also brought with him from Tasmania specimens of Spjhceroma gigas. Dr. Chilton found some of his N e w Zealand specimens free, but others " on a large Spharoma (probably S. obtusa Dana) in Port Chalmers." The following description refers to the specimens found at the Falkland Islands on Sjrfueroma gigas (or lanceolatum). This association has been spoken of as parasitic or semiparasitic. Apparently the small isopod makes use of the large one as a kind of floating island, affixing its eggs to it, and in adult life still clinging on but doing no harm to its animated lodging, which occasionally accommodates some minute zoophytes on similar terms. Body narrowly elliptical, peraeon wider than head or pleon, but almost parallel-sided except under the influence of the developing ova, when also the sides of the segments become less widely separated than before. The sides on the upper part are fringed with small hairs. The pleon has a very small first segment, followed by a rounded shield, fringed with minute hairs and slightly projecting obtusely between the uropods. Head widest at the eyes, obtusely projecting between the first antennae; in dorsal view the epistome obtusely promiuent in advance of the rostral projection. Eyes very small, wide apart, about at middle of the lateral margins of the head, each with only two crystalline cones set in dark pigment (see figure in Beddard's Beport). First antenna? |
