The hypostoma fig. 31 is of so transverse a shape that the breadth much surpasses the height, the former being 6 millim., while the latter attains only 3,5 millim. The anterior margin is so much arcuated and sloping backwards that it forms an obtuse angle. The side wings are triangular and acuminated and from them a thick pad runs backwards and forms the posterior margin. Below the largest field of the exterior surface the maculæ rest on a ridge having a much elongated, vermiform shape and sunk in the surface (fig. 32) a little more than three times longer than broad. In its shape it approaches much to the hypostoma of Bum. insignis HALL as delineated by SALTER pl. 27 fig. 7. In another, undetermined Bumastus (pl. II figs. 47, 48)[40] the hypostoma (from Klints, Othem, isle of Gotland) is of a more elongate obovate form, the anterior margin elevated, rounded, the terrace lines faint, the tubercles are larger than in the former Bumasti, oblong, curved, beanshaped, evenly rounded and smooth. [Footnote 40: Probably the same as Bum. sulcatus pl. XII fig. 12 in my paper on the Trilobites of Gotland 1885.] Another of the new species is one that LILJEVALL has found at Korpklint near Wisby (Pl. II figs. 41-46). The hypostoma is more elongate than transverse with the anterior margin regularly arcuated, by far not so prominent as in B. sulcatus and the former. By a shallow groove the exterior surface is divided in two fields, the anterior one the largest and covered with a few, distantiated, concentric terrace lines. The posterior field is smooth, nearly even and the maculæ lie just in the groove, with their axis oblique to the longitudinal axis of the hypostoma, beanshaped and smooth. The cephalic eyes show in a horizontal section hexaedral white walls enclosing a dark space in which some indistinct radii emanate, fig. 41 _a_. In the vertical sections the prisms are narrow and elongate and the integument by far not so thick as in Bumastus sulcatus, fig. 42, 43. The border zone of the eye in this (fig. 41) as well as in B. sulcatus, as seen in horizontal sections, agrees with that of the Asaphidæ. =Bumastus= sp. inlet. Pl. III fig. 1, 2. In a detached piece of limestone, found in Gotland, at Norderstrand, near Wisby, two hypostomas and a free cheek lay embedded along with a coral of the genus Acantholithus and a Bronteus probably belonging to a new species. As the coral has not been found above the uppermost beds of the Lower Silurian it is probable that the trilobites also are derived from the same horizon.