The interesting image, as given by the agglomerated eyes, is represented in the magnified [figure 43 Plate III]. The lenses lie there separated from each other at much varying distance, some in close contact. The presence of the delicate covering membrane is clearly seen, being of white colour contrasting with the black, glossy lens. It is much lacerated and only preserved around the periphery. The size of the ocelli is on an average 0,5 mm., a little one has 0,3 mm. The surface between the ocelli is most finely granulated. The granules scarcely attaining the fourth of the granules in Dalm. vulgaris.
In a vertical section the regular biconvex lenses are seen to be covered with the extremely thin integument, which is a direct continuation from the test. The test between the lenses is perforated by some longitudinal tubes, as usual in the skeleton of the trilobites. We have not found any hypostoma with the maculæ.
Dalmanites obtusus Ldm.
We have not succeeded in finding any hypostoma, but as the structure of the cephalic eyes is sufficiently well preserved, we here describe it. The lenses seen from the surface look globular, and in a vertical section they are ovate and in a horizontal circular. They are covered by a very thin and delicate membrane, that envelops their superior moiety completely and between the eyes it is enclosed by the surrounding test and growing out from it. In the horizontal section, [fig. 45], it looks as a circular frame around the lenses and the membranes of two contiguous lenses sometimes lie so close, that they entirely fill up the interspace between the lenses, leaving only a narrow slit between them marking their boundaries. The space between the lenses, fig. 46, is porous, being perforated by tubes, which continue vertically down through the shell of the cheek.
Dalm. sclerops Dalman.
Commonly this species has been ranged with Phacops, but it is evident that it as to the conformation of its glabella and the head in general is highly discrepant, and in these respects is more concordant with Dalmanites, though still deviating as for instance in the pygidium and some details of the head. Therefore it may be justified with Friedr. Schmidt[41] to consider it as a generic division, though not, as he has it, as an independent genus, but as a subgenus of Dalmanites.
[41] Revision, I, p. 76.