292 Dr. F. A. Bather — Eocene Echinoids from Sokoto. 



III. — Eocene Echinoids from Sokoto. 



By F. A. Bather, M.A., D.Sc, British Museum (Natural History). 



(PLATE XI.) 



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. K. 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 tempera- 

 ture, and rendering it very difficult to follow the course of the 

 sutures. The appearance of these and the other specimens show& 

 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. In each case 

 there is a larger and better preserved specimen referred to as A, 

 and a smaller one referred to as B. 



[The MS. of tliis paper was sent in on March 14th, 1904. After the proof had 

 been received, Captain Foulkes, E..E., kindly presented to the British Museum 

 a further collection of fossils from this region. It included two more specimens of 

 the Plesiolampas, referred to as C and D ; and twelve more of the Hemiaster, lettered 

 according- to their decreasing size from C to 0. The accompanying label reads: "In 

 bed of indurated chalk running into grey limestone underlying laterite. Found near 

 road just above Tamaske, where it descends from plateau." These specimens have 

 confirmed the main conclusions already set down, while affording a wider basis for 

 the diagnoses. Beyond this, a few allusions or illustrations are all that it has been 

 possible to introduce at this more than eleventh hour. — June 9th, 1904.] 



Plesiolampas Duncan & Sladen, 1882. 



Pal. Ind., ser. xiv, vol. i, pt. 3, Foss. Ech. W. Sind, pp. 9, 54, pis. i, xiii-xv 

 (non Flesiolampas, Pomel, 1883, " Genera des Ech.," p. 62). 



The two specimens agree entirely with the diagnosis of this genus 

 of Cassidulidae (subfam. Echinolampadinse) as drawn up in the 

 above-quoted work, and as repeated in P. M. Duncan's " Revision 

 of the Echinoidea" (J. Linn. Soc. Zool., xxiii, p. 193 ; 1889). They 

 have not the crenulate and perforate tubercles of Oriolampas 

 Munier-Chalmas. They differ, however, from the six species which 

 Duncan & Sladen described from the Eocene of Sind, and I am 



