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. 
Tzxt-FiaurE 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, 0.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 
