R. Bullen Newton — Egyptian Newer Tertiary Shells. 405 



Ostrea cucullata, Ficlieur : Desc. Geol. Kabylie du Djurjura, 1890, 



p. 382. 

 Ostrea cucullata, var. Byzacena, P. Thomas, " Desc. quel. Foss. 



Tunisie" : Explor. Scient. Tunisie, 1893, p. 21, pi. xiii, 



figs. 6-11. 

 Ostreola Forskali, and vars. undulatior, perrostrata, suhcucullaia, 



persacellus, F. Sacco : Moll. Tert. Piemonte, pt. xxiii 



(1897), p. 16, pi. V, figs. 1-3 and 6-12. 



Description. — Shell oblong in shape, with plicated valves. 

 The lower or convex valve deeply excavated, of variable width, 

 with sometimes nearly parallel sides, and furnished with an 

 elongate, straight, or curved ligamental rostrum, with its summit 

 usually directed backwards, and bearing a moderately deep 

 triangular fossula ; interior of more or less rectangular form, and 

 ornamented externally with a few slightly-elevated radial costse 

 crossed by a regular series of growth-lines. The upper valve is 

 depressed, somewhat lamellose, oblong, frequently narrow at the 

 ligamental area, exhibiting on the outer surface some obscure 

 longitudinal jDlications ; the muscular-scar impressions are super- 

 ficial and scarcely perceptible. 



Eemarks. — The Egyptian specimens referred to this species are 

 exactly comparable, not only with the living representative as it 

 occurs off the shores of the Red Sea, but also with some Italian 

 Pliocene forms that have been examined in the British Museum 

 (Natural History) — No. 80,943 — and which are labelled as 0. undata, 

 the equivalents of Bern's 0. cucidlata. Much more elongate liga- 

 mental rostra appear to distinguish specimens from the Pliocenes of 

 Tunis, Montpellier, and the Rhone Basin, the Tunis specimens being 

 also more numerously plicated than others. It is undoubtedly a most 

 variable mollusc, and authors are pretty generally agreed that it 

 should embrace 0. ForsJcali and 0. cornucopicB of Chemnitz, as well 

 as Lamai'ck's O. undata as figured by Serres. Certain distinctions 

 have been pointed out in this species which are said to be more or 

 less constant at the various localities where it has been found, thus 

 giving rise to the introduction of a number of varietal names by such 

 writers as Thomas, Fontannes, Viguier, and Sacco ; but although 

 these details are carefully worked out, they do not appear to be 

 adapted for general application. Under 0. Forshali, Chemnitz 

 alludes as far back as 1785 to the discovery of this mollusc in 

 a fossil state in Egypt by Professor Forskal. From late Tertiary 

 deposits near Cairo, Fuchs has described and figured an oyster called 

 0. pseudo-cucullata, which cannot possibly be separated from Bom's 

 species ; it corresponds exactly with an example of similar 

 dimensions from the Pliocene (Astian) of Italy. In confirmation of 

 this opinion, it is satisfactory to know that Dr. Schweinfurth came to 

 the same conclusion some yeai-s since, and the fact was published by 

 Sir William Dawson in his paper on " The Geology of the Nile 

 Valley " (Geol. Mag., 1884, p. 298). The specimens are of variable 

 dimensions and somewhat fragmentary ; they occur in a soft, green, 



