_D. Mac Coyi_ BARR. Supl., pl. 13 f. 32. This magnificent hypostoma belongs to the same group as D. micrurus HALL as to which we may hesitate whether there not be a double pair of maculæ above each other near the posterior border. In this species, however, there is the transverse lower groove and above probably the two maculæ united by a groove so closely as to resemble the lower groove. _D. micrurus_ J. HALL, Pal. N. Y. III pl. 74 fig. 20. Shows, as it were, a double pair of maculæ, very like D. spinifer BARR. _D. rugosus_ BARR. pl. 24 f. 23. The two maculæ in the ordinary place, without being united by a groove. _D. socialis_ BARR. pl. 26 f. 21. Rather of an uncommon shape, not so triangular as in the other species, the two maculæ distinct as narrow slits. P. 553 »Vers l'extrémité du corps central, on aperçoit de chaque côté, près du bord, une impression oblique, alongée et arquée». _D. spinifer_ BARR. Pl. 25, fig. 20. A large beautifully preserved hypostoma, shows what I think we positively must interpret as a double pair of maculæ close above each other. As stated above there is reason to believe that in other species of Dalmanites there also are indications of four maculæ, though not so evident as in this species. BARRANDE says nothing about this remarkable feature. =Dalmanites imbricatulus= ANGELIN. Pl. III figs. 43, 44. 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. Pl. III figs. 45, 46.