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as a rule, very small and sometimes greatly reduced in number. In the male,
the more or less complete fusion of the 1st segment of mesosome with the ce-
phalon is a very pronounced character, and moreover the larva in the last (Cryptonis-
cian) stage exhibits several well-marked peculiarities first pointed out by Dr.
Hansen. All the hitherto known forms are found parasitic on Schizopoda belonging
partly to the family Euphausiidoe, partly to that of the Mi/Mce. We know
at present of only 4 genera belonging to this family, 3 of which will be treated
of below.
Gen 1. DajUS. Kr0yer, 1842.
Leptophryxus, BuchhoJz.
Generic Characters. Body of adult female very tumid, slightly curved
ventrally, with the lateral parts greatly expanded and more or less projecting in
front beyond the cephalon, middle part of dorsal face sub-depressed and distinctly
segmented. Metasome abruptly contracted and divided into 6 segments, the last
carrying 2 small juxtaposed lamellae, the uropoda. Oral area comparatively
broad, semicircular. Antennae distinct, and of normal structure. Maxillipeds
extended anteriorly, as in the Bopyridae. Sternal plate of moderate size, trigonal
in form. Incubatory plates present in the normal number (5 pairs),
last )air
much the largest. Legs short and thick, exactly alike. First pair of pleopoda
forming 2 rather large lamellae occurring immediately behind the last pair
of in-
cubatory plates; the succeeding pairs rudimentary. Adult male with the meta-
some undivided. Parasitic on species of the genera My sis (sens, strict.) and
Cynthilia (Siriella), being attached to the ventral face of the last segment of
mesosome, between the incubatory lamellae of the host.
Remarks. This genus was established in the year 1842 by Kr0yer. to
include a peculiar parasite found by him on a species of J///*/N. The genus
Leptophryxus of Buchholz is unquestionably identical with Kr0yer's genus, and
was founded upon the very same species. We know as yet of only 2 species be-
longing to this genus. One of these will be described below, the other having
been briefly recorded from the Challenger Expedition by the present author,
under the name of Dajus siriellce. A 3rd species, it is true, has been estab-