Chr. Boeck gives in Mag. for Naturvidenskaberne Bd 8, 1828, in his paper on the Trilobites on the plate fig. 16 the hypostoma of a Bohemian species with well developed concave maculæ, probably a cast. He compares it with the Entom. bucephalus of Wahlenberg, but says he cannot explain its nature.
The maculæ of P. oelandicus, pl. V, fig. 34, are tubercles, oblong, smooth, and have invariably an oblong scar along the centre, where probably once a thinner membrane, as in the cephalic eyes of Calymmene, contained the lenses.
Peltura M. Edw.
Peltura scarabæoides Wahlenb.
We have given a figure of the hypostoma, showing two large, elongated tubercular maculæ or rather resemblances of such, as they are covered with terrace lines as well as the rest of the surface. They have, however, the same position as real maculæ might have, but are directed in a line parallel with the longitudinal axis of the hypostoma. The cephalic eyes have been described above at [page 29].
Phacops Emmrich.
Maculæ figured of Phac. (Acaste) Downingiæ. Salter Monogr. pl. 2 fig. 34 b, p. 25 »high up on each side a small tubercle».
Phac. rana Hall Pal. N. Y. vol. VII, pl. VIII A, fig. 18. Hypostoma with the large commalike maculæ high up.
Of the following species Ph. cephalotes and Ph. macrophthalmus belong to the genus Phacops proper, while Phac. quadrilineata, as well as Ph. Downingiæ are of a quite different generic type. The name Acaste proposed for them is not good as Leach in 1817 named a Cirrhiped as Acasta.