The hypostoma is in so far deviating that the terrace lines have a nearly vertical direction and in this respect much resemble those of the Phillipsiæ and the Proeti. The maculæ, near the exterior angles of the border groove are pear- or spoon-shaped with the apex directed downwards and outwards, and in consequence the longitudinal axis quite opposite to that of the usual direction. The surface is smooth, a little concave. No structure has been discovered. From the pointed apex a slightly elevated ridge runs along the posterior border of the hypostoma and joins the apex of the other macula. =Paradoxides= BRONGN. The oldest record of any hypostoma at all amongst the trilobites is that given by WAHLENBERG in his Petref. Suecana (1818) p. 37 Tab. 1, fig. 6, which he, however, considered as the head of the trilobite which he named Entomostracites bucephalus. Figures with maculæ have been given of _Par. Davidis_ SALTER Mem. Geol. Survey Dec. XI pl. X, fig. 3, a fine figure of a hypostoma with two large oblique maculæ. LINNARSSON in »de undre Paradoxideslagren vid Andrarum» pl. II fig. 2 delineates a gigantic hypostoma with two crescentic tubercular maculæ, having 10 mms. in length. _Par. Forchhammeri_ ANGELIN Pl. II fig. 3. BRÖGGER, Paradoxidesskiffr. vid Krækling tab. II fig. 10 two marks somewhat different from ANGELIN'S figure. LINNARSSON 1. c. pl. I figs. 9, 10 two hypostomas with maculæ. _Par. Tessini_, var. _Wahlenbergi_ ANGEL. Pl. I a, fig. 1 b. _Par. Tessini_, var. _oelandicus_ ANG. Tab. I a, fig. 2 b. ANGELIN'S figure of this hypostoma is incomplete in so far that he had not found the peculiar falciform horns on both sides of the posterior border. Pl. V, fig. 33. _Par. rugulosus_ CORDA has, according to BRÖGGER, Krækling, pl. II fig. 2 two long, straight callosities, probably corresponding to the maculæ in other Paradoxidæ. 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. Pl. III fig. 42. 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.