In a former paper I gave a section of part of Down Cliffs, near Seatown, Dorset; but I had obtained no evidence of the palæontological contents of the Bed 19. Partly, no doubt, on account of its position (only a little above the Marlstone), and partly on account of its blue colour, this bed has been called by Day and by H. B. Woodward “Upper-Lias Clay;” and I think that I am correct in saying that this term has, in this country, usually signified those argillaceous deposits which, occupying a very similar position above the Marlstone, contain the fauna of the Falciferum - and Commune -zones. Last summer I had an opportunity of further examining Down Cliffs, and, after some search, was enabled to procure sufficient evidence to show what is really the correct horizon of the clay- or marl-bed in question. The evidence consisted of Ammonites of the genus Dumortieria ; but their condition was unsatisfactory for preservation, since they were little else than impressions or casts in the marl, and were often crushed. I was, however, able to preserve a few specimens; and, having frequently met with similar Ammonites in the Cotteswolds, I was able to determine even those specimens which I could not preserve. One species I could make out with certainty, namely Dumortieria radians . Accompanying this, was a wider-ribbed form of the same genus—a genus so easily recognized by the peculiar straightness of the ribbing. The wider-ribbed species was most probably Dumortieria Levesquei. Now, species of the genus Dumortieria