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Fam. 2. Dajidae.
Characters. Body of adult female perfectly symmetrical,
shield-like, and
more or less curved ventrally, the 3 chief divisions being only slightly indicated,
and the segmentation, as a rule, only visible in the middle of the dorsal face,
lateral parts of mesosoine more or less expanded and hollowed, to receive the
ova and embryos. Ventral face exhibiting in front a comparatively small de-
pressed area, defined anteriorly by the frontal margin, laterally by the closely
crowded coxal plates. Antennae of different structure in the different genera.
Buccal mass conically produced, and containing the styliform mandibles. Maxillse
obsolete. Maxillipeds lamellar, without any terminal joint, turned sometimes an-
teriorly, sometimes posteriorly. Behind them a more or less developed sternal
plate, occupying the. floor of the above-mentioned area. Incubatory plates com-
paratively small, sometimes greatly reduced in number, and scarcely at all par-
taking of the formation of the marsupium, which constitutes two separate
cavities bounded by the lateral walls of the body itself. Only 5 pairs of
legs present, these being densely crowded together around the oral area. Pleopoda
generally rudimentary or wholly absent. Uropoda distinct or wanting. Adult
male narrow linear, with the cephalon and 1st segment of mesosome coalesced,
rnetasome simple or imperfectly segmented. Last larval stage
with the basal
joint of the antennulse produced behind to a long tooth-like projection, antennal
flagellum 5-articulate ; oral cone terminating in a circular sucking disk; 1st pair of
legs shorter and thicker than the others, last pair with 2 groups of delicate, diverging
spinules on the palmar edge ; uropoda with the rami subequal. Parasitic on Schizopoda.
Remarks. This family forms, as it were, a transition between the Bopy-
ridce and Cryptoniscidas, and is chiefly characterized by the shield-like, perfectly
symmetrical body of the female, the total absence in the same of the 2 posterior
pairs of legs, and the close crowding together of the 5 anterior pairs, which
are arranged around a small depressed ventral area situated quite in front.
The mode in which the marsupial cavity is formed, is also very
different from
that found in the Bopyridce. Whereas in the latter this cavity is formed exclu-
sively by the largely developed incubatory plates, in the forms belonging
to the
present family it is bounded by the lateral walls of the body itself, and therefore,
strictly spoken, constitutes 2 separate cavities, more or less approximate on the
ventral face, but never confluent. The incubatory plates only serve for closing
the anterior and posterior openings leading to these cavities, and are therefore,