In the animal kingdom the attribute of bigness has come to be regarded as one of the prerogatives of the vertebrates. On this account, invertebrates seldom receive credit for having a size of more than a fraction of a cubit, and are looked upon as objects to be held in the hand or viewed under a lens. As a matter of common experience, and probably also of congratulation, large invertebrates are rare, and some whole classes cannot furnish a single individual measuring more than a few inches in greatest diameter.

The fossil to be discussed in the present memoir is the specimen which formed part of the classical material used in the discussion which was carried on amongst British geologists during the second half of the present century. So important a controversy could hardly be restricted to the geographical limits of England alone.

Although the present summary covers the same ground reviewed only a few months ago by the junior bearer of the name which will always be gratefully and prominently remembered in connection with the scientific conquest of Madagascar, the following lines will show that, short as the interval has been, the new additions are not unimportant.

An interesting collection of shells, numbering more than fifteen hundred specimens, obtained by the officers of the Geological Survey of Egypt from the raised beach deposits of the Red Sea, has recently been examined by the writer at the request of Captain Lyons, R.E., the Director—General of the Survey.

Nautilus truncatus was described and figured by J. Sowerby in the “Mineral Conchology,” vol. ii, p. 49, pl. cxxiii, April, 1816, his description and remarks being as follows:—

“Spec. char. Thick, flatted, plain, umbilicate ; back flat, mouth elongated, four-angled : siphuncle nearest to the inner margin of the septum.