Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/200

 2. Notes on some new Crustaceans from the Lower Eocene of Portsmouth. By Henry Woodward, Esq., F.G.S., F.Z.S., of the British Museum.

[Plate IV.]

Having been favoured by Messrs. C. J. A. Meyer and Caleb Evans with the opportunity of examining three new Crustaceans recently obtained by them from the Lower Tertiary Deposits exposed during the excavations for the "Dockyard Extension Works" in Portsmouth Harbour, I beg to submit the following notes thereon.

I. Family Corystidae. (Genus Paloeocorystes, Bell.)

This family, represented at the present day by the genus Corystes common on our own coast, and in the Chalk, Greensand, and Gault by the genera Paloeocorystes and Eucorystes, has now been discovered in the Lower Eocene, at Portsmouth, by Mr. Caleb Evans, F.G.S.

The specimen (see Plate IV., figs. 1 a, b), although far from perfect, is sufficient to indicate at once the genus to which it belongs, namely Paloeocorystes, and also that it is specifically distinct from those occurring in the Cretaceous rocks, already described by Prof. Bell and others *. The carapace measures one inch in length ; but (both its anterior and posterior borders having been injured) it was, originally, probably nearly one-fourth of an inch longer. In breadth it measures 10 lines. Some portion of the anterior (orbital and suborbital) border can still be traced out ; but the rostrum is quite destroyed. The surface of the carapace is smooth and devoid of ornamentation, save a few widely scattered and very minute puncta ; but where the delicate cortical layer has been removed, the carapace presents a finely granular structure. The two sigmoid markings, observable on the carapaces of all the Corystidae are also clearly to be seen in this example.

On the underside the branchiostegal pieces (br) are traceable, also the basal joint (m) of one of the maxillipedes (see Plate IV. fig. 1 b).

I propose to name this form Paloeocorystes glabra. Previously to the discovery of this crab no species of Paloeocorystes had been met with in any bed younger than the Maestricht Chalk, where a species named P. (Notopocorystes) Mulleri has been noticed by Count von Binkhorst, which much resembles P. glabra, save that the sigmoidal markings seen on the latter are absent in the former species. (See Plate IV. fig. 2.)

This is the second family of Crustaceans living at the present day, and met with fossil in the Maestricht Chalk, which I have had the pleasure of recording as occurring also in the Eocene of the south of England†.


 * See Prof. Bell's Monograph on the Fossil Crustacea of the Gault and Greensand, Palaeontographical Society, 1862, vol. xiv. p. 11, pls. ii. & iii.

† See British Association Reports, Norwich, 1868, on the Occurrence of Callianassa Batei in the Upper Marine Series, Hempstead, Isle of Wight, p. 75, pl. 2. fig. 4.