240 W. G. RIDEWOOD. 



siderably since tlie stage shown in h, and the axes are less 

 bluntly tipped. The interval between the right and left 

 plumes of the first pair is not relatively, but absolutely less 

 than in earlier stages — all these figures are drawn to the 

 same scale of magnification. The exigencies of pictorial 

 delineation demand that the structures nnder consideration 

 be drawn flat ; it is well to bear in mind, therefore, that, 

 while the structures represented near the median line of the 

 figure are on the antero-ventral surface of the "body " of the 

 bud, just above the buccal shield, the lateral parts (plumes 6 

 and 7, and lateral parts of the post-oral lamella) are set high 

 up the sides of the "body." The figure if cut out and bent 

 back would give approximately the correct relation of the 

 parts. 



In the adult the right and left seventh plumes are as close 

 together as are the right and left first plumes. The line of 

 plume-bases in the adult, when viewed from the front, is an 

 ellipse, incomplete on the upper side ; and the line of the 

 attached edge of the post-oral lamella is another ellipse 

 similarly incomplete. The two ellipses join where they are 

 incomplete (see text-fig. 8). The parts seen are, of course, 

 at very different distances from the observer ; the base of 

 the fifth plume is in the middle distance, the base of the 

 first plume is nearest to the observer, and the mid-ventral 

 part of the post-oral lamella farthest away. The stalk of the 

 buccal shield and the mouth lie in the middle distance 

 between the two ellipses, and the anus dorsal to both (com- 

 pare text-fig. 8 and text-fig. 5, d). 



The seventh plumes of the adult, and in some polypides 

 the sixth plumes also, do not arise directly from the " body " 

 of the polypide, but are processes of a paired lophophoral 

 upgrowth, which is connected with the " body " at the base 

 of the fifth plume and the more ventral parts of the collar- 

 outgrowths (see " Cephalodiscus," '"Discovery" Expedi- 

 tion Reports,^ 1907, p. 31, last paragraph). 



Late buds of Ccphalodiscus nigrescens are extremely 

 rare in the material at my disposal. Possibly after the stage 



