NKWrON : LOWER TERTIARY MOLLUSCA OF TilK FAYUM. iO 



interesting raolliiscau remains from the Qasr el Saglia lieds, among 

 tliera being a giaut form of the freshwater shell Lanistes antiquus, 

 which is worthy of placing on record. Its measurements are diam. 85, 

 height 50 mm. Tlie largest example previously known appears to 

 be that mentioned by Dr. Blanckenhorn, exhibiting a diameter of 

 53 and a height of 28 mm. The specimen under consideration is 

 a natural cast formed of a yellowish-red sandy matrix, with no 

 vestige of shell-structure remaining; small fragmentary ostreiform 

 shells are seen in the rock material filling up the aperture. It belongs 

 to the depressed forms of Lanistes, of which Olivier's AmimUaria 

 carinata may be regarded as the type. The volutions, numbering 

 about five, are fairly deep and laterally compressed, while the base 

 shows considerable inflation, being besides furnished with a wide 

 and deeply excavated umbilical region, in which the inner whorls 

 are well exposed. According to Mr. Beadnell's section of the Qasr 

 el Sagha Beds (p. 51 of his memoir), this mollusc occurs in Bed 18, 

 associated with marine shells, hence we may assume that the deposits 

 were laid down under estuarine or brackish-water conditions. The 

 Qasr el Sagha Series belongs to the Upper Mokattam or Parisian 

 division of the Eocene, and are consequently of Lutetian age. This 

 species was originally figured by Orlebar from the ' Yellow Limestone ' 

 of the Mokattam Hills as Cirrus, and subsequently by Bellardi as 

 Ampullaria subcarinata from the i*^uramulitic beds in tlae neighbourhood 

 of Cairo. Without any reference to these two writers, Mayer-Eymar, 

 nearly fifty years later, claimed the shell as belonging to the recent 

 form of Chemnitz's Helix terrestris BoUeniana contraria, and so figured 

 and described it as Ampullaria {Lanistes) Bolteni, from the Upper 

 Parisian of Egypt (near Dime, and the north of Mokattam), being 

 found in the Alectryonia Clot-heyi beds of that formation. Dr. Blancken- 

 horn next discussed the shell, pointing out its wrong determination 

 as a recent species, and established for it the new name of Lanistes 

 antiqims. In the latest account of this fossil Dr. Oppenheim restored 

 Bellardi's name, recognizing it as Lanistes suhcarinattis. From the 

 synonymy now offered it is apparent that Ampullaria subcarinata, 

 as determined by Bellardi, is no longer tenable, because much earlier 

 in the last century G. B. and James Sowerby (Genera of Shells, 1822) 

 had used the same name for a recent shell from the Congo Biver 

 of Africa. It follows, then, that Dr. Blanckenhorn's Lanistes antiqxms 

 should be the recognized name for this shell. The genus Lanistes 

 appears to be entirely restricted to African freshwaters at the present 

 day ; and the fossil species now referred to, in all probability, represents 

 the ancestral form of L. carinatiis, Olivier, sp. {— L. BoUeniana), 

 which, exists in Birket el Qurun, in the Nile, near Alexandria, and 

 at numerous other places on the same river or its tributaries, as far 

 south, as the Victoria Nyanza (according to Professor E. von Martens. 

 Deutsch-Ost-Afrika, vol. iv, p. 169, 1898), Lake Dembea, etc., and 

 occurring also in some profusion in the younger Post-Pliocene deposits 

 of the Fayum depression. 



Formation. — Lutetian (Middle Eocene). 



Locality. — Near Qasr el Sagha (Dr. C. "W. Andrews). 



