1. Parabolina (oldest division of the Olenus slates). Olenus. Liostracus. 2. Eurycare. Leptoplastus. 3. Peltura. Sphærophthalmus. Ctenopyge. 4. Cyclognathus (uppermost). Acerocare. [Footnote 27: Om Agnostusarterna vid Andrarum.] It is already in the second division that we find the earliest oculate genus in Eurycare and in the higher strata. Sphærophthalmus and Ctenopyge with enormous hemispherical eye balls, while Olenus and Parabolina, their earliest predecessors, probably were blind. We have not amongst hundreds of specimens of these genera found a single specimen showing an ocular globe covered with facets. Olenus and the nearly related genus Parabolina are found in innumerable specimens in the thinly laminated alumschists of Scania and other provinces of Sweden. But rarely a perfect head shield, or nearly so, is to be found with the free cheeks in place. If so, the semicircular scallop in the free cheek is entirely filled up by the posterior lobe of the facial ridge and there is no place left for any eye.--If we, again, find a non compressed glabella and fixed cheeks likewise, the facial lobe (-»eye-lobe») is in some elevated so much as to leave a little space between it and the scallop of the free cheek, which space must have been an empty lacuna if not filled up by an eye ball. But it may also be that the free cheek has been somewhat put out of its order and that consequently some space has been left between it and the free cheek. It is quite as much with older genera, as Solenopleura especially, in which the posterior lobe of the facial ridge (_vulgo_ »eye lobe») has attained a great development, and in which one just could expect to find a sphærical eye resting between the elevated lobe and the scallop. The elevated rim of this scallop does not in fact constitute a proof for its having clasped an eye as the elevated scallop in Sphærophthalmus did. In Paradoxides, again, in Ellipsocephalus, where there is absolutely no trace of an eye ever having been present, whenever you succeed to find the free cheek in juxtaposition with the fixed cheek it is evident that the elevation of the scallop rim is due to the impact of the posterior lobe of the facial ridge. In many specimens of Dolichometopus and Corynexochus etc. no free cheeks have ever been found and to judge by the shape of the facial ridge it may be concluded that these also were deprived of eyes.