A^oL. 3] Juday. — Ostracoda of the San Diego Region. 15 



Family HALOCYPRIDAE. 



Valves sub-equal, very thin and flexible, composed of two 

 tunics which are scarcely adherent except at the edges; hinge 

 margin straight, almost or entirely toothless; antero-dorsal ex- 

 tremity produced into a more or less prominent rostrum or beak 

 with a subjacent rostral sinus. Eyes wanting, or present only 

 in an abnormal condition. A frontal organ, or tentacle which 

 usually has a club-shaped extremity or capitulum, projects for- 

 Avard in the median line between the antennules. The anten- 

 nules are unlike in the two sexes ; in the female, weak, indistinctly 

 jointed, immobile, and bearing a fascicle of sensory setae ; in the 

 male, larger, more distinctly jointed, mobile and bearing a long 

 seta. Antennae natatory, bearing a secondary branch which has 

 a prehensile appendage. Mandibles well developed, biting plate 

 dilated and toothed at the apex; mandibular palp large, four- 

 jointed, the basal joint with a large dentated lobe which is in con- 

 tact with the biting apex of the mandible; terminal joints bear- 

 ing setae or spines. Second pair of feet larger than the others 

 and unlike in the two sexes; third pair very small. Caudal la- 

 minae short and clawed on the posterior margin. Copulatory 

 organ of the male single, sinistral. 



Genus Archiconchoecia Miiller. 



Shell with a well developed rostrum which is similarly shaped 

 in both sexes. Groups of glands open almost symmetrically on 

 the two halves of the shell, somewhat below the postero-dorsal 

 angle. Antennules in both sexes very similar, in the male some- 

 what stronger, only indistinctly jointed; first and second joints 

 fused together; with six sensory filaments at the end, of which 

 four belong to the ultimate and two to the penultimate joint. 

 Secondary branch of the antennae without mammillary process ; 

 the five long setae of the last two joints similar to each other, 

 all sensory. Chewing part of mandible without distinct setae 

 and spinous teeth, armed only with minute spinules. First foot 

 similar in both species, stronger in the male, but without any 

 marked differences in the setae of the last joint. Branchial plate 



