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Remarks. This peculiar form may at once be distinguished from our
other Tanaids, at least in the female sex, by the rudimentary
condition of the
metasome. In both sexes, moreover the structure of the chelipeds and uropoda
may serve for recognizing the species.
Occurrence. I have met with this form occasionally together with other
Tanaids in several places, both on the south and west coasts of Norway, as far
north as Kvalo, in depths ranging from 50 to 150 fathoms.
G-en. PseudOtanalS, G. 0. Sars, 1880.
Generic Characters. Body short and stout, not very different in the 2 sexes,
with the cephalosome more or less contracted in front, and having no distinct
ocular lobes. The 3 anterior segments of mesosonie much shorter than the 2
succeeding ones. Metasome not broader than the mesosonie, and composed of 6
well-defined segments. Eyes imperfectly developed, or altogether wanting. Superior
antennae of same structure in the 2 sexes, very narrow, 3 -articulate ; inferior an-
tennae almost of same size as the superior. Mandibles comparatively small, cut-
ting part in the right mandible simple, minutely serrulate, in the left one
provided with a rather large secondary lamella, molar expansion in both mandi-
bles very narrow, styliform. Maxillipeds with the masticatory lobes coalesced.
Chelipeds large, of a similar structure in the 2 sexes, hand very much elongated,
fingers narrow and acuminate. Pereiopoda slender and elongated; 1st pair somewhat
differing from the others, which are subsimilar in structure, each having a remark-
ably strong, cultriform spine at the end of the carpal joint inside. Pleopoda
sometimes wanting in female Uropoda biramose, both rami well-defined and bi-
articulate. Incubatory pouch formed by only 2 lamellae, issuing
of the 4th pair of pereiopoda.
from the bases
Remarks. This genus agrees with the genus Tanais in the less conspicu-
ous sexual difference, and in the structure of the incubatory pouch, but otherwise
differs very materially, both as to its outward appearance, and to the structure
of the several appendages. It comprises as yet 7 species, 3 of which belong to
the Norwegian fauna, and will be described below. Of the other 4, the one,
P. Willemoesi (Studer), has been taken off the Kerguelen Islands, the second, P.
mediterranea G. 0. Sars, at Spezia. and the other 2, P. affinls and P. crassi-
cornis Hansen, in the Kara Sea.