396 R. Bullen Newton — Egyptian Cretaceous Shells. 



labrum ; columella provided with three plications ; anterior canal 

 short, twisted ; spiral angle diminishing with growth. 



Dimensions. 



Length ... ... ... ... ... 120 mm. 



Spiral angle 20° to 15° 



Sutiu-al angle ... ... ... ... 85° 



The present specimens, although rather fragmentary and 

 crystalline, are sharp, well-defined, and exhibit both internally 

 and otherwise all the characters of this species. One piece shows 

 the early condition of the spire with an angularity of 20°, while 

 a later portion has a spiral angle of 15°. An oval section seen in 

 a transverse fracture of another specimen clearly indicates a com- 

 pression of the spire. The width of the whorls increases from 

 1 mm. to 16 mm. 



Remarks. — In his monograph on the Geology of Egypt, Professor 

 Mayer-Eymar refers to the great abundance of a new Perinea, under 

 the name of N. pyramidarum, in rocks of Senonian age occurring 

 W.N.W. of the Great Pyramid. He regards it as an intermediate 

 form between N. nobilis and N. Biichi, having oblique ribs, more 

 or less obsolete, on the earlier part of the spix'e, with a tendency 

 to a marginal thickness of the whorls. Although no figure 

 accompanies his brief remarks, there is little doubt that this shell, 

 with the characters alluded to, is identical with D'Orbigny's Nerinea 

 Bequieniana, which according to the original account was not 

 peculiar to European areas alone, but had also been found in Egypt 

 by a M. Lefebvre. 



Some of the specimens are encrusted with concentric chalcedony 

 (" Beekite "), the matrix being a yellowish-white limestone. 



Horizon. — Turonian. 



Distribution. — Various localities in the west and south-west of 

 France ; environs of Jerusalem ; W.N.W. of the Great Pyramid ; 

 Abu Eoasch : Coll. Geol. Surv. Egypt (No. 63, Box No. 32c) ; aud 

 Coll. British Museum, G. 11,485. 



LAMELLIBRANCHIATA. 



Genus OSTKEA, Linnseus. 

 Systema Naturae, 1758, ed. 10, p. 696. 

 Type. — 0. edulis, Linn^us. 



OSTKEA AGANTHONOTA, Coquancl, 



Ostrea acanthonota, Coquand : "Mon. genre Os^rea Cretace," 1869, 



p. 103, pi. xxxviii, figs. 1-4. Walther, " L'Apparition 



de la Craie environs Pyramides": Bull. Inst. Egyptien, 



1888, ser. 2, No. 8, p. 8. 



Description. — Shell subequivalve, oblong, convex, arched ; 



valves ornamented with prominent ribs, which commence a short 



way from the beaks and afterwards bifurcate ; ribs regular, augulose, 



imbricated, obtusely spined, and separated by deep and wide 



grooves; summits ostreiform, equal; muscular scar nearly central, 



anteio-laterai. 



