The discovery of Chiton Loftusianus at Tunstall Hill, in 1844, by Messrs. Loftus and King, introduced the family Chitonidæ into the List of the Permian Fauna*. For several years this species remained its sole representative; but in 1856 another species was found in the same locality, and in the course of the next year it was described in this Journal under the name of Chiton Howseanus . Until a recent date these were the only Permian species that were known to belong to this group. In the present communication, however, it is intended to describe four additional members, three of which appear to belong to the subgenus Chitonellus , and one, probably, to Chiton proper; so that instead of two, the Chitonidæ will have six representatives in the fauna of the Permian epoch. The two species already known will also be noticed, as a few characters pertaining to them seem to have been overlooked in the descriptions and critical observations of which they have already been the subject. In the spring of the present year (1858), while pursuing palæontological researches in the shell-limestone of Tunstall Hill, I found some obscure fossils associated with others which I referred to the Calyptræa antiqua of Mr. Howse. for some time the true nature of the former was a great puzzle to me; and it was not until a month or two ago that I became aware that both those which I had referred to C. antiqua and C. antiqua itself were all plates of various