“Transversely rhomboidal, moderately gibbose, width four times the length; sides flattened, regularly attenuating to the very acute cardinal angles; cardinal area broad, flat; mesial fold wide, defined, angular, smooth; about sixteen to eighteen slightly convex, simple, smooth ribs on each side of the mesial fold, becoming indistinct as they approach the cardinal angles, so as to leave nearly a third of the length of the sides smooth.”

The origin of the Lower Trias is evidently a question of interest to the readers of the Geological Magazine. Professor Bonney, in an article, to the tone of which no exception can be taken, criticizes the view which I have ventured to put forth, and very properly supports his own. It would be impossible and a waste of paper and type for me to traverse all his statements, as in many cases my reply would amount to little more than a reproduction, in a different form perhaps, of the arguments already made use of. There are, however, one or two points on which I should like to express myself, and there are some misconceptions that require clearing up.

The Fossil Fishes of the English Portlandian Formation are as yet almost unknown, and every small contribution to the subject is thus of interest. Ischyodus Townsendi, Microdon pagoda, the partially described Caturus angustus, an undetermined species of Thrissops, and an undescribed species of Mesodon, appear to be the only forms hitherto recorded; and to these may be added a large bony fish allied to Ditaxiodus, represented by jaws in the British Museum.

The late Prof. Louis Agassiz, whilst on a visit to Halifax with Prof. John Phillips, during the years in which he was preparing his “Recherches sur les Poissons fossiles,” identified the caudal extremity of a large species of Cœlacanth fish to which he appended the name of Cœlacanthus Phillipsii in honour of his friend. The specimen is from a large “baum-pot,” as the calcareous nodules are locally termed, obtained from the Lower Coal-measures. This specimen was found at the Swan Bank Pit at Halifax, and, so far as I know, is the only one which has been discovered. The surface exposed by splitting the nodule is 0.295m. diameter, and the part of the fish preserved extends across it; it consists of the caudal portion of a large individual, which, had it been perfectly preserved, would have been between four and five feet in length.

This paper is intended as preliminary to one shortly to follow on the nature and origin of the banded structure in these rocks. I have deemed it necessary to treat of the present subject as introductory to the other, giving my own views as to what I believe to be the true origin and relations of these rocks to each other, as these seemed to me to have a very direct and important bearing on the question of their banded structures.

I cannot conclude this paper without remarking that none of the views therein are held dogmatically, and expressing the hope that former observers will renew their attention, and fresh ones take up the investigation of this complicated, yet interesting area. The difficulties are great, among which is the origin of the banded structure, in the rocks herein dealt with, which in my next paper I shall try to explain on the grounds of segregation, arising from, or taking place during the cooling of the common magma out of which all these rocks seem to me to have been formed.