Vol. 70.] REMAINS FROM THE YICTORIA NYANZA REGION. 191 



pretation of the shell, however, it is necessary to consult the 

 figures and description of Dr. W. Kobelt as published in 1911, 

 although exception must be taken to that author's recognition of 

 it under the genus Jfeladomus. 1 It is more correct to regard 

 Meladomus as embracing those species of reversed shells allied 

 to Lanistes that have produced spires, and are besides mostly 

 imperforate or simply furnished with a slit-like opening — as 

 opposed to the true Lanistes, which exhibits a spreading and 

 depressed spiral region, as well as a deeply-excavated umbilical 

 cavity. The present species, therefore, to which the fossils are 

 referred, forming the type of Lanistes of D. de Montfort, 1810, 

 should not be mistaken for a member of Gray's later genus, 

 Meladomus. The fossils, numerously represented in the collection, 

 consist chiefly of matrix-casts, composed of dull greyish clays or 

 marls frequently tinged or mottled externally with dark reddish 

 brown. 



They are particularly characteristic of Beds 14 & 15, being also 

 found in Beds 21, 22, & 32, although much less sparingly and 

 of smaller size. Occasional shell- structure has been preserved, 

 in which the finely-carinate sculpture of the spire can be traced 

 together with the growth-striations. As in the recent shell, 

 the peripheral carina of the fossil form gradually disappears in 

 its later development, the last whorl exhibiting considerable in- 

 flation and roundness. The height of the spiral region may also be 

 mentioned, as showing slight variation both in recent and in fossil 

 examples. It is a significant fact that no opercula of this mollusc 

 have been found, their absence being probably due to the extremely 

 delicate character of that organ, as also on account of its corneous 

 texture, which would favour its entire dissolution during the 

 processes of fossilization. 



Distribution. — This species is known from the younger post- 

 Pliocene deposits of the Fayum depression in Egypt (specimens in 

 the British Museum and the Cairo Museum), and is found living in 

 the Nile (near Alexandria, etc.), Birket el Qurun, Lake Dembea 

 (Abyssinia), and the Tana Biver in British East Africa. It 

 apparently does not belong to the present-day fauna of the Victoria 

 Nyanza, no specimens having been found among a large series of 

 shells brought back from that lake by Dr. Oswald ; nor are there any 

 examples in the British Museum collection. Dr. E. von Martens 2 

 has referred doubtfully to its occurrence in the Victoria Nyanza; 

 while Mr. E. A. Smith 3 has regarded as unreliable Dr. H. Dohrn's 

 statement 4 that the species exists in those waters. According, 



1 Meladomus was originally proposed by W. Swainson (' A Treatise on Mala- 

 cology ' 1840, p. 340), but without recognizable type or description. Its proper 

 adoption was due to J. E. Gray (Proc. Zool. Soc. London, 1847, p. 148), who 

 selected as its type G. B. Sowerby's Paludina olivacea ; therefore to Gray 

 must be accredited the authorship of this genus. 



- ' Beschalte Weichthiere Ost-Afrikas— Deutsch-Ost-Afrika ' vol. iv (1898) 

 pp. 169, 290. 



3 Ann. Mag. Nat. Hist. ser. 6, vol. x (1892) p. 121. 



4 Proc. Zool. Soc. London, 1864, p. 117. 



