I.—On the Discovery of Cyclosphæroma in the Porbeck Beds of Aylesbury

Abstract

In December, 1890, I had the good fortune to describe a new Sphasromid discovered by Mr. Thomas Jesson, B.A., F.G.S., in the Great Oolite of Northampton, which I named Cyclosphæroma trilobatum (see Geol. Mag., 1890, Dec. III, Vol. VII, pp. 529–533, PL XV). This specimen, which is redrawn on the accompanying PI. XIV (Fig- 1), is remarkable for its rounded outline, which induced me to apply to it the name Cyclospharoma.Great was my joy when, in March last, I received from my friend Mr. E. J. Garwood, M.A., F.G.S., another Jurassic Isopod, of which both the intaglio and the, relievo had been obtained by him in the Purbeck beds near Aylesbury. This remarkably beautiful Crustacean proves to be a more perfectly preserved example of the same Sphseromid which I had described in 1890, from the Great Oolite of Northampton, and it needs but to compare Figs. 1 and 2 upon our Plate to perceive that in Fig. 1 the thoracic segments are much compressed together posteriorly, and that the hinder part of the telson is wanting; otherwise the resemblance between it and the newly-found and much more perfect example from the Purbeck beds of Aylesbury (PI. XIV, Fig. 2) is unmistakable.A reference to the diagnosis of the genus (as given in Geol. Mag., 1890, p. 530) will show that it must now be amended in consequence of the discovery of the more complete specimen by Mr. Garwood.