221 



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 mesosome more or less expanded and hollowed, to receive the 

 ova and embryos. Ventral face exhibiting in front a comparatively small de- 

 pressed area, denned anteriorly by the frontal margin, laterally by the closely 

 crowded coxal plates. Antennse of different structure in the different genera. 

 Buccal mass conically produced, and containing the styliform mandibles. Maxillae 

 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, 

 metasome 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 Cryptoniscida?, 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 Bopyridw. 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, 



