Vol. 67.] KAINOZOIC MOLLTTSCA VttOTl CYUKNA1CA. 629 



that region being mostly grey, sandy-looking limestones containing 

 well-preserved forms of Operculum. Further pectinoid shells col- 

 lected at Wadi Umzigga and Birlibah, and exhibiting a much simpler 

 costal structure, are associated with a matrix varying from a com- 

 pact cream-coloured limestone to a yellowish arenaceous rock with 

 minute blackish mineral grains and externally weathering to a light 

 reddish-brown, which has yielded examples of Lepidocyclina ele- 

 phantina Munier-Chalmas, 1 together with other orbitoidal organisms 

 and Ojperculina. In none of these rocks mentioned as Aquitanian 

 has the true Nummulites been observed. 



Aquitanian deposits have not been recognized by Dr. Blancken- 

 horn as occurring in Egypt, 2 the lowest Miocene determined being 

 the Langhian or Burdigalian stage, which is developed in the 

 Moghara district of the Libyan Desert. A similar statement would 

 probably apply to the other divisions of Northern Africa, although 

 in Eastern Africa and Madagascar, according to A. de Lapparent's 

 manual, 3 Aquitanian beds occur with Lepidocyclina and Litho- 

 tliamnion. As stated previously, some of the species recorded here 

 as Aquitanian resemble the ' Schioschichten ' fauna of Northern 

 Italy, but there are others which exhibit a facies belonging more 

 to the Burdigalian or Helvetian type, such as jSSquipecten zitteli, 

 2E. camaretensis, and jE. scabrellas, and yet occurring in matrix 

 similar to that associated with Pecten vezzanensis, JEquipecten 

 cf. pasinii, and Spondylus cisalpinus. This mixture of forms is 

 interesting although not unknown, as Dr. Oppenheim's memoir on 

 the ' Schioschichten ? refers to some pelecypods which are more 

 usually recognized as Burdigalian or Lower Helvetian, rather than 

 Aquitanian. 4 



Pelecypoda. 



Ostrea cf. caudata Minister. (PI. XLIV, fig. 1.) 



Ostrea caudata Minister in Goldfuss, 'Petrefacta Germanise ' 1833, vol. ii, 

 pi. lxxvii, figs. 7 a-1 cl & p. 17. 



Remarks. — The specimen thought to be related to this species 

 is a lower valve, the exterior of which is in a very worn condition. 

 It is of deltoid contour, very convex, and with a well-rounded 

 posterior border ; the anterior side is elevated, more or less abrupt, 

 distinctly truncated near the ventral corner, and possessing an 

 attachment cavity which occupies more than half the area of the 

 shell. The surface exhibits a lamellar structure which appears to 

 be crossed at distant intervals by very obscure radial plications. 

 The interior is tilled with matrix. 



Dimensions (lowervalve). — Length = 48 millimetres ; height = 

 50 mm. ; depth = 20 mm. 



1 See Mi'. Chapman's paper on the Foraminifera of this collection (p. 660). 



2 Zeitschr. Deutsch. Geol. Gesellsch. vol. liii (1901) pp. 52, etc. 



3 'Traite de Geologie ' 5th ed. (1906) p. 1597. 



4 Zeitschr. Deutsch. Geol. Gesellsch. vol. lv (1903) pis. viii-xi & pp. 98-235. 



