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Limnoria lignorum (Eathke).
(PI. XXXI.)
Cymothoa lignorum, Ratlike, Skrifter af Naturh. Selsk. Vol. 101, PI. 3, fig. 14.
Syn: Limnoria tcrebrans, Leach.
untinata, Heller.
Specific Characters. Body, when fully extended, about 3 times as long as it
is broad, and almost semi-cylindric in form, slightly tapering in front. Cephalon
nearly globular, and partly covered above by the 1st segment of mesosonie, front
obtusely rounded. First segment of mesosome considerably longer than the others
and rather deep, forming below, on each side, a rounded lobe projecting over the
lateral faces of the cephalon. Coxal plates fringed with ciliated bristles, the 2 {in-
terior pairs oval quadrangular, the 4 posterior ones considerably larger, and pro-
duced to an acute corner pointing backwards. Metasome considerably exceeding half
the length of the mesosome, and scarcely narrower, epimera triangular, projecting
laterally; terminal segment about the length of the other 5 combined, and very
broad, almost elliptical in form, posterior edge evenly arcuate and finely ciliated.
Eyes comparatively small, rounded, with a limited number of large cornea;. Supe-
rior antennee somewhat stronger than the inferior, with the flagellum extremely
small, 3 -articulate, and carrying a dense fascicle of long sensory filaments.
Inferior antenna1 with the flagellum about half the length of the peduncle, and
composed of 5 articulations, the 1st of which is much the largest. First pair of
legs somewhat larger than the next succeeding ones, but otherwise of the very
same structure, meral and carpal joints in most of the legs strongly tubercular
inside. Last pair considerably more slender than the others, and without any
tubercles. Dactylus in all legs distinctly bi-articulate, the 1st joint having at the
end inside, a bidentate unguiform spine. Uropoda with the .basal part strongly
tuberculated outside, and projecting between the rami to an acute projection, outer
ramus short, unguiform, turned outwards, inner sublinear, about the length of
the basal part, and terminating in a dense bunch of slender bristles. Colour
light greyish brown, with darker brown pigmentary ramifications. Length of adult
animal 5 mm.
Remarks. This form was described by Kathke as early as in the year
1799 as Cymothoa lignorum. By subsequent authors, it has generally been re-
corded under the name given to it by Leach, viz., Limnoria terebrans. The Lim-
noria imcinata of Heller, from the Adriatic, is undoubtedly identical with the
northern species.
Occurrence. I have found this form not infrequently in the Christiania
Fjord, at Drobak and Moss, boring in immerged pieces of wood. A single