1904] Description of Paracartia Gram. 7 



lamellar expansion obtusely truncated at the tip and fringed at the 

 anterior corner with delicate hairs. The genital orifices are placed 

 far apart just at the base of the above-mentioned expansions; and 

 immediately in front of them the seminal receptacles, with their 

 short twisted ducts, are distinctly observed (see fig. 5). The 2nd 

 segment is conspicuously instricted at the base, and gradually widens 

 distally. The 3rd segment is still broader and is transversely 

 truncated behind. 



The caudal rami (see fig. 4) are comparatively short, but råtner 

 broad and pronouncedly asymmetrical, the right ramus being con- 

 siderably larger than the left. They both originate with a broad 

 base from the last segment, and slightly taper towards the tip, 

 which is transversely truncated. The marginal setæ are not much 

 elongated; they are 5 in number on each ramus, 2 of them issuing 

 from the outer edge, the 3 others from the tip. The middle apical 

 seta, however, on both rami is peculiarly transformed, constituting a 

 strong, almost naked spine, which on the right ramus is somewhat 

 coarser than on the left. As in the genus Acartia, moreover, a 

 very delicate and finely ciliated seta springs from the dorsal face 

 of each ramus at some distance from the inner corner. This seta 

 originates from a bulbous base and is undoubtedly of a sensory nature. 



To the ventral face of the genital segment, a narrow bottle-shaped 

 spermatophore (fig. 7) is generally found attached. This sperma- 

 tophore is always accompanied by a thin plate, which on each side 

 forms a wing-like expansion folding upwards so as partly to encom- 

 pass the urosome (see figs. 1, 2, 4). A somewhat similar formation 

 has been described by the present author in Epischura baiMlensis, 

 and the problematic plate mentioned by Dr. Giesbeecht in Acartia 

 verrucosa Thompson, is unquestionably of the same nature. The 

 intimate connection of this plate with the spermatophore in the 

 present form, is easily proved by dis.section (see fig. 6). 



In immature female specimens, the urosome exhibits a somewhat 

 different appearance (see Pl. III, fig. 8). Thus the genital segment 

 has the lateral parts quite evenly rounded, and all the caudal setæ 

 are normally developed, the innermost but one differing from the 

 others only in its greater length. In such specimens, moreover, 

 the lateral expansions of the last segment of the metasome are 

 not nearly so large as in adult specimens, and are nearly rectangular 

 in form. 



The eye is of large size and located near the frontal edge (see 



