Vol. 70.] REMAINS FEOil THE VICTORIA XTAXZA REGION. 195 



rounded, and obtuse apical region. There are some partly-preserved 

 remnants of ornamentation, which appear to be quite characteristic 

 of the genus, exhibiting a series of closely-set, irregular, and 

 longitudinally-oblique costulations. It is probable that this fossil 

 belonged to a species like A. panthera of Ferussac, the "well- 

 known East African (Mombasa, etc.) shell, which might have had 

 dimensions such as 120 by 60 millimetres. 



Occurrence. — The specimen is of solid limestone, and much 

 mineralized at the base ; it was obtained from ' pale green-grey 

 clay ' in Bed 24, accompanying opercula of Ampullaria. 



L o c a 1 i t y. — Kachuku. 



Burtoa cf. xilotic a (Pfeiffer). (PI. XXX, fig. 13.) 



Bulimus niloticus Pfeiffer, Proc. Zool. Soc. London, 1861, p. 24 (not figured). 

 Limicolaria nilotica Pfeiffer, ' Novitates Concholog.' vol. iv (1870) pi. ex, figs. 1-3 



& p. 5. 

 Achatina nilotica Jickeli, Xova Acta Acad. Caes. Leop.-Car. vol. xxxvii (1874) 



p, 151. 

 Hnrtoa nilotica Bourguignat, ' Moll. Afrique Equator.' 1889, p. 89 ; E. A. Smith, 



Proc. Make. Soc. London, vol. i (1895) p. 323. 

 Livinhacia nilotica E. von Martens, ' Bescbalte Weichthiere Ost-Afrikas — Deutsch- 



Ost-Afrika' (K. Mobius) vol. iv (1898) text-figures, pp. 94-98; W. Kobelt, 



Abhandl. Senckenberg. Naturf . Gesellsch. vol. xxxii (1909) p. 69. 



He marks. — The specimen referred to this form is supposed to 

 represent the summit portion of an individual that may have 

 originally been 80 or more millimetres long. It is of helicoid 

 appearance, and consists of four whorls which are steep and of plano- 

 convex character ; the apical region is smooth and obtuse, while the 

 later whorls are ornamented with closely-set oblique costulations 

 of rather irregular and wavy design, crossed by 'obscure spiral 

 striations. An obtuse medio -angulation surrounds the base, which 

 would form the junction of the succeeding whorl. The suture-line 

 is well impressed, but slightly interrupted by the thickened ends of 

 the costulations. The specimen is quite robust and solid, except at 

 the basal surface, where the shell- structure becomes extremely thin 

 and delicate, a feature most probably caused through protection by 

 the covering of the next volution. No remains of the periostracum 

 are preserved. 



Dimensions in millimetres: length =16; diameter =15. 



From its obtuse apical region and the peculiar characters of the 

 sculpture, there is a great probability that the fossil belonged to a 

 large Achatinoid shell, similar to Burtoa nilotica, a well-known 

 species of Equatorial Africa, as has been suggested to the writer 

 by Mr. E. A. Smith. It was this mollusc that Pfeiffer originally 

 described and figured under Bulimus and Limicolaria respectively, 

 and it was subsequently selected by Bourguignat as the type of his 

 genus Burtoa} a name which has about a month's priority of 

 H. Crosse's genus Livinhacia, founded on the same type. 2 



Distribution. — Burtoa nilotica lives near the sources of the 

 White Nile ; as also in the region of the Victoria Nyanza, the 



1 'Moll. Afrique Equator.' 1889, pp. 88, 89. 



2 Journ. Conchyl. vol. xxxvii (1889) p. 105. 



