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



age, identified by Mr. Gauthier as Plesiolampas. That a large parb 

 of the intervening area was filled by the Lutetian sea is proved by 

 the occurrence of Nautili and Echinoidea, believed by Captain Gaden 

 to be of the same species, at Zinder and in Damergu, where the 

 beds are more marly. Professor de Lapparent further recalls the 

 occurrence of Echinolampas of Lutetian age at Dakar [near Cape 

 Verde], and supposes the inward extension of an Atlantic Gulf on 

 this side. If the Eocene limestones and marls ever extended 

 northwards, they have now been denuded, and in their stead are 

 found outcrops of Cretaceous rock, which have in Damergu yielded 

 to Captain Gaden an ammonite allied to the Turonian Mammites 

 and Vascocerns, while 450 km. north of Lake Chad, at Bilma, 

 Colonel Monteil found an echinoid of Maestrichtian age, described by 

 Mr. V. Gauthier' as Noetlingia Monteili. This fossil also indicated 

 a connection with north-west India. The same connection may 

 have remained open for several geological ages ; and while, on the 

 one hand, the Lutetian sea may have extended northwards over 

 Bilnia and even into the Libyan desert, so on the other hand the 

 Cretaceous rocks may pass southwards and underly the Lutetian of 

 Sokoto and Damergu. 



The modesty of the English officers of the Niger-Chad Boundary 

 Commission will be the less offended, and my own awkwardness 

 the less exposed, if Professor de Lapparent will permit me to borrow 

 his concluding paragraph, all but one woi'd : " Je crois devoir 

 terminer en exprimant une vive gratitude a I'egard des vaillants 

 oflficiers qui, sous un ciel de feu, au milieu de fatigues et de pre- 

 occupations de toute sorte, ne negligent pas de recueillir au passage, 



pour le plus grand bien de la Science , des documents 



d'un pareil interet." 



DESCEIPTIOX OF PLATE XI. 



Plesiolampas Sahar.^2. 

 Fig. 1. Tubeiciilar oruameut on an iuteiTadius of abactiual surface ot D : x lOdiam. 

 ,, 2. Apical system of A : x 10 diani. 



,, 3. Tubercular ornament on an interradius of actinal surface of D : X 10 diam. 

 ,, 4. Distal. end of petal IV of A, surface abraded : X 3 diam. 

 ,, 5. Distal region of petal III of A : X 3 diam. 



Hemiaster sudaxensis. 



Fig. 6. Abactinal surface of A : nat. size. 



,, 7. Apical system of A : x 10 diam. 



8. Posterior view of A : nat. size. 



9. Distal end of petal V of A, showing fasciole : X 5 diam. 



10. Distal region of petal II of A : x 5 diam. 



11. Left side view of A : nat. size. 



,, 12. Actinal surface of specimen I, mainly to sbuw normal heteronomy : 



X 2 diam. 

 ,, 13. View of H from left posterior interradius, to show peripetalous and lateral 



fascioles : nat. size. 



1 Bull. Soc. Geol. France (4), i, p. 189 ; 1901. See also A. de Lapparent, C.K. 

 Acad. Sci. Paris, cxxxii, p. 388; 1901. 



