98 R. BULLEN NEWTON on 



DIMENSIONS. 



Smallest Largest 



example. example. 



Length ... ... ... ... ... 25 ... 113 millimetres 



Height ... ... 20 ... 75 



Diameter (closed valves) ... ... 20 ... 60 



DISTRIBUTION. The Upper Mokattam deposits of Egypt (Bartonian), and 

 the Nigerian deposits. 



OCCURRENCE. Cuttings Nos. i, 5, 6, 10. 

 COLLECTORS. Sir John Eaglesome and Mr. Kitson. 



Family CORBULID^. 

 Corbula rugosa, Lamarck. 



PLATE 7, figs. 14-18, 

 Corbula rugosa, 



Lamarck : Ann. Mus. Hist. Nat. (Paris), 1806, Vol. 8, p. 467 (not figured) ; Deshayes : Desc. Coq. 

 Foss., Paris, 1824, Vol. i, pi. 7, figs. 16, 17, 22, p. 51 ; J. de C. Sowerby in F. Dixon's "Geology of 

 Sussex," 1850, p. 89 ; Deshayes : Suppl. Desc. Coq. Foss., Paris, 1857, Vol. i, p. 226 ; Cossmann : Ann. 

 Soc. R. Mai. Belgique, 1886, Vol. 21, p. 48 ; R. B. Newton : " Syst. List, &c.," 1891, p. 89. 



Corbula lyonsi. 



Oppenheim : Palaeontographica, 1906, Vol. 30, part 3, pi. 18, fig. i, p. 196. 



REMARKS. This form of Corbula occurs in great abundance in the Nigerian 

 deposits. It is strongly globulose, both valves, especially the lower, being well 

 excavated ; the umbonal regions are rounded and the summits much incurved. 

 In the ridged ornamentation of the lower valve it somewhat resembles C. ficus, of 

 Solander, from the Bartonian deposits of England, although differing in the 

 absence of a prolonged posterior end, which is as stated in the original diagnosis, 

 brevissime rostrata. The posterior area is marginally carinated within and has a 

 strongly striated surface, features which are well seen in examples from the 

 Anglo-Parisian Basin (Bracklesham Bay and near Paris). The upper or smaller 

 valve is concentrically striated but much less prominently than the other, being 

 generally smoother, it moreover is furnished with distant radial striations 

 apparently only seen in well preserved specimens, those from Bracklesham Bay 

 showing them rather obscurely, whereas Parisian examples, such as are available 

 for study, appear to be destitute of such a structure. The Egyptian shell, 

 C. lyonsi, of Oppenheim must, I think, be regarded as the European species, 



