398 R. BuUen Neivton — Egyptian Cretaceous Shells. 



OsTREA ViLLEi, Coquand. PI. XVI, Figs. 1-3. 



Ostrea Villei, Coquand : " Geol. Paleont. Constantine," 1862, p. 231, 



pi. xxii, figs. 1-4. 

 0. homilicaris, Coquand : ibid., p. 230, pi. xxi, figs. 4-6. 

 0. Villei, Coquand : " Mon. genre Ostrea Cretace," 1869, p. 27, pi. iv, 



figs. 1-8 ; pi. V, figs. 1-4. 

 0. homilicaris, Coquand : ibid., p. 24, pi. ii, figs. 12-15. 

 0. Villei, Peron, '•'Deso. Moll. Foss. Cretaces Tunisie" : Explor. Sci. 



Tunisie, pt. ii (1891), p. 182. 



Desckiption. — Shell of subtriangular or triangular contour, in- 

 equivalve ; lower valve convex, ornamented with numerous regular, 

 bifurcating ribs, sepai'ated by deep grooves and sometimes provided 

 with a smooth surface of attachment at the umbonal region ; upper 

 valve of less convexity than the lower and similarly ornamented ; 

 muscular impression large, oval and ventral. 



Dimensions. 



Upper valve. Lower valve. 



Medium -sized single valves — Height ... 45 mm. 40 mm. 



Length ... 45 ,, 40 ,, 



Diameter ... 10 ,, 21 ,, 



Several isolated valves of this species are in the collection, and 

 vary somewhat in their characters. They all, howevei", preserve the 

 more or less triangular shape and the bifurcated character of the ribs. 

 The lower valve is considei'ably arched, whilst the other is only 

 moderately convex and more often depressed ; most of the valves 

 exhibit the characteristic enlargement of the pallial area, with 

 frequently decided lateral extensions. 



Eebiarks. — Coquand's two species, Ostrea homilicaris and 0. Villei, 

 have been united under the latter name, on account of their similar 

 characters, by M. Peron. A careful comparison of specimens in the 

 British Museum, and a study of the figures of this species given by 

 Coquand and others, appear to confirm the correctness of the present 

 determination, although the shell does not seem to have been hereto- 

 fore recorded from Egypt. It occurs in soft and hard varieties of 

 a fawn-coloured sandstone. This harder matrix, identical with that 

 containing Trigonoarca multidentata and Protocardia hiseriata, shows 

 also a fragment of bone of probably reptilian origin, but which 

 Mr. A. S. Woodward informs me is not determinable.^ Other 

 examples of this oyster are met with in a grey, compact limestone, 

 encrusted with "Beekite," being the same material as contains 

 A.rctica Barroisi and Ostrea Lijonsi. 



Horizon. — Turonian. 



Distribution. — Algeria; Tunis; and "Sheet 33": Coll. Geol. 

 Surv. Egypt (No. 1,043, Box No. 55c). 



^ It may be incidentally mentioned that remains of Mosasanms have been recorded 

 from the Cretaceous rocks of Wadi Ouh, near El Radsieh, Egypt, by Figari Bey 

 (" Studii Scientifici Egitto," vol. i, 1864, p. 29), which were subsequently identified 

 by Zittel as Mosasaurus mosensis ("Beit. Geol. Pal. libysch. Wiiste " : Palseonto- 

 graphica, pt. i, 1883, p. Ixxvii), but, as far as can be ascertained, no figures or 

 description of this species have yet been published. 



