BARRANDE regards the whole ridge as a prolongation of the eye and the tubercle at its posterior extremity as the eye itself.[22] But, again, in page 399 he says »Sa surface (of the eye) est toujours mal conservée, pour nous permettre de voir si elle était réticulée.» And he also confounds the ridge, »filet» as he names it, with the eye itself, and the first faint beginnings of this ridge in his fourth stage he considers as the eye.[23] By a partly schematical figure of the free cheek (fig. 25) he places the eye on this cheek, and in the same manner in fig. 29, »restaurée d'après divers fragments» he figures a reticulated surface of the eye on the free cheek, outside the tubercle. I have sought for a reticulated surface on sufficiently good specimens, but never found any, and I must consider Sao as one of the blind genera. BARRANDE himself also in the table on the eyes of the trilobites places Sao in the group with »Surface visuelle inconnue», p. 131. [Footnote 22: Page 383 »l'œil argue est prolongé par un filet en relief, vers le front de la glabelle».] [Footnote 23: p. 389.] [Illustration: (0 is new, added here to supplement fig. I.)] BRÖGGER has also succeeded[24] in finding a series of small larva, which he considers as belonging to a species of Liostracus. As the figures drawn by BRÖGGER twenty five years ago may now be very little known, I here reproduce them with the kind permission of the Editors of »Geologiska Föreningens Förhandlingar», where they were published in 1875. This development proceeds nearly upon the same plan as in Sao. The first stage, however, (I) seems to be much earlier than any of Sao, the rhachis or glabella consisting of an unsegmented ridge of more primitive appearance. Before this first stage of BRÖGGER'S larva a still older phase of development can be imagined, (0) a simple rounded, smooth head shield without any indication of a glabella at all. This stage might correspond to the head of certain species of Agnostus, as A. glandiformis, A. nudus, which have no glabella. This stage 0 is also valid for the larva of Sao. Several stages are evidently wanting between I and II, in the later of which the thickened glabella is divided in four segments. In III we have six segments, all these three stages consisting only of the ovate head with narrow fixed cheeks. In IV the pygidium has been added to the primitive head, but the segments of the glabella have been reduced to four and in V slightly altered in shape In VI, again, we see the head with five glabellar segments and scarcely the first sign of the facial ridge. Between VI and VII there must be links missing, as the change can not be so abrupt, and likewise between VIII and IX as in VIII there are still no free cheeks nor any facial ridge. This interesting discovery of BRÖGGER confirms, together with those of several other authors[25], the supposition that the development of the later Cambrian and older Silurian forms is a quite