Nigerian Eocene Mollnsca. 109 



CONCLUSIONS. 



A final study of the Mollusca from these Nigerian deposits, which consist 

 of rather more than 70 species, is in favour of their Middle Eocene or 

 Lutetian origin, and probably its later part on account of the prevalence of 

 Bartonian forms. Many of the species are prolifically represented. The only 

 Cephalopod collected, Belosepia sepioidea, although occurring throughout the 

 Eocenes is more characteristic of Lutetian than of any other part of the 

 series. Among the Gastropods, of which some 40 forms have been recognised, 

 the large Surcula is important as agreeing in every way with S. ingens from 

 the Upper Mokattam Beds of Egypt which are of Bartonian age. * A form of 

 Pteropurpura allied to tricarinata suggests likewise its Lutetian horizon, 

 while such species as Cornulina minax, Bonellitia cf. evulsa, Neverita cf. 

 calvimontana, Sinum cf. clatkratum, Calyptraea crepidularis, all support a 

 similar geological age. The occurrence of Bulbifusus, hitherto known only 

 as an American Eocene Gastropod, is also of great interest since it tends to 

 prove a stratigraphical relationship between the Middle Eocene deposits of 

 Alabama, which has yielded that mollusc, and those of Southern Nigeria. 

 Most of the new Gastropods described exhibit affinities with species that are 

 more or less characteristic of Lutetian times, among which may be mentioned 

 particularly Turritella mauryana, a form with resemblances to T. mortoni, 

 also, from the Alabama Eocene. 



The Pelecypoda of these beds of which there are 30 different species show 

 similar horizonal results, as for instance the discovery of Raetomya sckweinftertki, 

 which until recently was only known in the Upper Mokattam deposits (Bartonian) 

 of Egypt. There are also the remains of an oyster closely allied to O. 

 marginidentata, a species confined to the Bracklesham beds of England and 

 therefore of Middle Eocene age, as well as a large rostriform oyster, 

 Crassostrea lugardi, which is closely related to C. soudanensis recently 



1 The Mokattam deposits of Egypt are divided into two groups, an upper and a lower. The older cr 

 lower beds are recognised as Lutetian, whereas the upper beds have been referred to as Bartonian in De 

 Lapparent s"Traite de Geologic," 1906, Ed. 5, p. 1542, and as Bartonian and Priabonian by Dr. W. F. 

 Hume in his " Explanatory Notes to accompany the Geological Map of Egypt " published by the Geological 

 Survey of Egypt in 1912 (p. 18), although previously the whole of the Mckattam limestones had been deter- 

 mined as of Lutetian age. 



