III.—Eocene Echinoids from Sokoto

Extract

It is fortunate that Captain Lelean not merely discovered these fossils at Garadimi in Sokoto, but that he had enough sense of their importance to spend some time and trouble in their collection, and that now he has generously presented them to the British Museum. The collection includes four echinoid tests, five natural casts of Mollusca, and a few rock-specimens containing Operculina and other Foraminifera. The Mollusca, so far as their state of preservation admits, have been determined by Mr. R. Bullen Newton as: 3 Lucina cf. gigantea Deshayes, 1 Voluta cf. cithara Lamarck, and 1 undetermined Gastropod. The Echinoidea were partly covered by an impure limestone closely adherent to the test. The portions not so covered were in many places considerably worn, and the calcite was split by cracks, probably due to alternations of temperature, and rendering it very difficult to follow the course of the sutures. The appearance of these and the other specimens shows clearly that they have been lying on the surface of the ground for some time, and, in fact, Captain Lelean informs me that they were not picked out of the solid rock, but from the talus at the foot of the cliff. The notable variations in the matrix of the different specimens are thus accounted for. None the less it will be seen in the sequel that all the specimens are consistent with the ascription of a Middle Eocene age to the mass of limestone from which they were derived. Of the four echinoids, two have been determined as belonging to the genus Plesiolampas and two to the genus Hemiaster.