VII. Summary: As the result of the iuvestigation forming the subject of this paper the following conclusions have been drawn:— The six crystals, the measurements of which are given in complete detail above, belong to the same species (sartorite) as that deseribed by vom Rath and Baumhauer. The faces observed on the ends of the crystals are referable to three distinct and non-congruent lattices, of which one is monoclinic and the other two are triclinic in aymmetry. The latter two are, however, twinned about the axis of symmetry so that in the case of a fully-developed crystal there are altogether five distinct lattices. The shear by means of which each lattice may be imagined to be tranaformed into the one adjoining it is constant in amount, but variable in direction. At the same time there is a perceptible difference in the constants defining the constituent lattices of the several lattices. The two crystals figured and described by C. O. Trechmann, together with a third described in this paper, belong to a distinct, though no doubt closely allied, species, which for convenience we have named sartorite-α. Sartorite and sartorite-α have probably the same chemical composition, and the relation between their morphological characters is parallel to that existing in the case of calaverite and krennerite.