studies on marine Oslracods 295 



First antenna: — The sensory bristle of the fifth joint (fig. 8) is somewhat thicker 

 proximally and grows narrow somewhat more abruptly distally than in the female; its nine 

 proximal sensory filaments are longer relatively and are thicker at the middle, rather spool- 

 shaped. Bristles of the seventh joint (figs. 9, 10): The b- and c-bristles are of about the same 

 relative lengths and have the same number of filaments, five and ten respectively, as in the female. 

 It is the three proximal filaments on these bristles that have suctorial organs. The proximal 

 one of these three filaments has no verruciform process distally of the sucker. The two others 

 are rather slightly stronger than the distal filaments and rather short relatively, of about the 

 same length as most of the latter ones; they have from five to seven small suctorial organs 

 distally, sometimes arranged rather irregularly; sometimes there is a small verruciform 

 process distally or proximally of these. The other filaments on these two bristles are on the 

 average somewhat longer than those of the female; the distal one on the c-bristle is exceedingly 

 short. Bristles of the end joint: The f- and g-bristles are subequal and about twice as long as 

 the shell (on one specimen, for instance, with a shell 6,5mm. long these bristles were 13 mm. long, 

 thus exactly double; in some cases they were somewhat shorter, in others even somewhat longer 

 relatively). In spite of this great length they have about the same number of filaments (from 

 19 to 22 were observed) as in the female; these filaments are also on the average somewhat 

 longer than in the female; the distal one is not short as is the case in the last-mentioned sex. 

 In other respects this antenna agrees with that of the female. 



Second antenna: — ■ This is considerably stronger than that of the female. 

 Protopodite: On some males with shells 6,5 — 6,6 mm. long this was 2,5 — 2,6 mm. in length. 

 Exopodite: In the males mentioned above this was 2,2 — 2,4 mm. long (in some females with 

 shells 6,6 — 6,7 mm. long this branch measured only 1,9 — 2,0 mm.); the natatory bristles some- 

 what, though only slightly, longer relatively than in the female. In other respects this limb 

 agrees very closely in both sexes. 



The mandible, maxilla and fifth limb are very like those of the female. 



Sixth limb: — This too shows very close agreement with that of the female, 

 but the bristles seem, however, to be on the average somewhat fewer, especially on the second 

 exopodite joint, on which only 20 — 25 ventral bristles were observed. This divergency seems, 

 however, to be of less importance when one takes into consideration the comparatively great 

 variability shown by this limb with regard to the number of its bristles. 



The seventh limb is like that of the female; the end comb sometimes seems, 

 however, to be somewhat weaker than in this sex. 



The furca, upper lip, rod-shaped organ and lateral eyes are 

 similar to those of the female. 



The penis agrees with G. W. MC'LLER's description. 



Remarks: — In spite of the incompleteness and uncertainty of G. S. Bi-t-VDY's original Diffcrenees from the 

 description of Cypridina castanea there can scarcely be any doubt that the form described by "'"''''"'' "'^'"''' ""■• 

 me above is to be referred to this species. — Although the original description is so deficient 

 there are, however, not a few differences that may be observed, but these are certainly to be 



