1911.] NATURAL SCIENCES OF PHILADELPHIA. 247 



Platynereis agassizi (Ehlers). PI. XV, fig. 19. 



Nereis agassizi Ehlers, Die Borstenwurmer, 1868, pp. 542-546, Taf. XXIII, 

 fig. 1. 



Besides several atokous individuals, two of which (station 4,559) 

 contain eggs, a large number of sexually mature epitokous examples 

 were taken at station 4,355 by means of a surface electric light and 

 dip-nets. Of the latter 83 were males and only 5 females. As the 

 latter have never been described, a brief description is here added. 



In general appearance they agree closely with the males, but average 

 somewhat larger, from 21 to 33 mm. long. The two regions of the 

 body of the two extremes measure, respectively, 5 and 16 mm. and 

 11 and 22 mm. long, and the segments number from 93 (28 + 65) to 

 131 (28 + 103), the anterior region of the female comprising, therefore, 

 seven more segments than that of the male, which has 21. One 

 female has only 27. 



The color is generally pale and faded, but shows indications of 

 transverse brown lines and posteriorly more distinct transverse rows 

 of spots. Some of the specimens exhibit the same yellow color an- 

 teriorly as shown by the males, but usually much paler. 



Prostomium almost exactly as in the males, the eyes, coalesced on 

 each side, scarcely perceptibly smaller, the palps and tentacles turned 

 almost as markedly ventrad. Peristomial cirri, so far as preserved, 

 have the same proportions as in the males and, also, as in the males, 

 are easily detached, so that many of them are wanting. One specimen, 

 however, in which all are present, has two dorsal cirri nearly equal, 

 both reaching XV, and the anterior ventral reaching to VI. There 

 is a very short caudal region of ten or twelve segments with few or no 

 swimming setse and a short, tapering, tubular pygidium often con- 

 stricted into two rings, quite different from that of the male in that it 

 bears four cirriform papillae in place of the whorl existing in the latter. 



The first five (on the smallest specimen four) notocirri only are 

 thickened and the slender distal end much less abruptly hooked than 

 on the males. First four neuropodia similar to those of the males. 

 Parapodia and setse of anterior region also as in the males. Posterior 

 parapodia differ from those of the males chiefly in the total absence 

 from both notocirri and neurocirri of the sense organs which cause 

 them to appear serrated, the cirri in the females being therefore quite 

 smooth, simple and tapered. 



Most of the specimens have shed the greater part of their eggs, but 

 one remains filled with them as far forward as the tenth setigerous 

 somite, inclusive, and a few have escaped into more anterior somites. 



