Fig. 3D–F.

Material.—Three pygidia, 0.4, 0.6, and 0.8 mm long (the latter estimated).

Description.—The pygidia are subsemicircular in outline and more than twice as wide as they are long. The axis is wider than the pleural fields, slightly tapering backwards, and broadly rounded posteriorly, not reaching the posterior margin. It consists of an articulating half−ring, two axial rings, and a terminal piece. The pleural field narrows backwards and has two shallow furrows extending almost to the postero−lateral margins. A very narrow, curving articulating facet is present on the antero−lateral margin. Three pairs of marginal spines, directed backwards and inwards, are present lateral to the posterior margin behind the axis.

Remarks.—In the smallest pygidium (Fig. 3F) the marginal spines are relatively longer than in the larger pygidia. The development of the surface sculpture can be traced from the smallest to the largest specimen. In the smallest specimen the ornament consists of granules, slightly elongated and, on the pleural fields, subparallel with the postero−lateral margin. On the axial rings these granules have coalesced into incipient transverse terrace lines. Less developed terrace lines are present at the posterior margin. In the next larger specimen (Fig. 3D) the terrace lines are much more distinctly developed on the pleural fields and behind the axis. In the largest specimen (Fig. 3E) the terrace lines are very well developed as raised ridges forming short, linked sections, but continuous behind the axis. On the terminal piece of the axis they are again continuous and subconcentric with the axial furrow surrounding the posterior end of the axis.