SHIELD OF CEPHALODISCUS NIGRESCENS. 



27 



at its extremity, and the stolon is attached relatively farther from this end of the 

 body and nearer to the buccal shield (fig. 15, plate 4). The end of the stolon bears from 

 two to five buds of various sizes, and thus resembles that of ordinary polypides. 



Buccal Shield. 



The outline of the buccal shield is that of an oval with indented sides 

 (text-fig. 9, C). The ventral surface is not flat, but has a raised central portion 

 separated from the anterior and posterior portions of the rim by shallow grooves. 



C. 



TEXT-FIGURE 9. A = Buccal shield of a bud of C. nigrescens with two pairs of plume-axes only ; B = Shield of a bud 

 with four pairs of plume-axes ; C = Shield of adult polypide of C. nigrescens. The figures are drawn to the same 

 scale of magnification (x 43). 



The anterior and posterior borders are deeply pigmented, and slightly in advance 

 of the inner dark border of the posterior part of the shield, but separated from it 

 by a pale band, is a well-defined red line, which is curved, and follows the 

 posterior half of the outline of the central and thicker portion of the shield. In 

 text-figure 9 the red line is represented by the firm black line that passes across 

 the shield (see also plate 3, fig. 8, b.s.). 



In a well-expanded shield, removed and mounted for examination under the 

 microscope, the antero-posterior diameter is slightly greater than the maximum 

 width, and the distance from the centre of the red line to the anterior edge of the 



