in Limestones from Sinai. 315 



Family NUMMULINIDiE. 



Subfamily NUMMULITIN^. 



Operculina, d'Orbigny [1826]. 



Operculina complanata (Defrauce), vai\ canalifera, d'Archiac. 



(PL XIII, Figs. 3a, 4a ; PL XIV, Fig. 12.) 



Operculina ammonea, Leynierie (pars), 1844 : Mem. Soc. geol. France, ser. ii, vol. i, 



p. 359, pi. xiii, fig. 11. 

 0. canalifera, d'Archiac, 1850 : Hist. Prog. Geol., vol. iii, p. 245. D'Archiac & 

 Haime, 1853 : Descr. Anim. groupe niimmulitique Inde, p. 182, pi. xii, 

 figs, la-c ; and vol. ii (1854), p. 346, pi. xxxv, fig. 6a ; pi. xxxvi, 

 figs. 15rt, 16a. 

 0. Ubijca, Schvrager, 1883 : Palceontographica, vol. xxx. Pal. Theil, p. 142, 

 pi. xxix (vi), figs. 2a-g. 



After a careful comparison of tbe various specimens of tbe large 

 and compressed forms of Operculina wbicb are often so abundant in 

 tbe nummulitic series and subsequent formations of Asia, Africa, 

 Euro^^e, and tbe West Indies, we bave arrived at tbe conclusion tbat 

 tbe so-called species, so numerously described and figured, can only 

 be regarded as varieties of tbe type form 0. complanata (Defrance). 

 Tbese varieties, nevertbeless, wben confined witbin certain limits of 

 cbaracters, determined probably by tbe influence of local conditions, 

 will prove of value in determining facies and minor series of strata 

 in given areas. 



O. complanata, var. canalifera is cbaracterized by tbe rapid 

 increase in tbe widtb of tbe wborls in tbe last turn or so. Tbe 

 surface of tbe central area of eacb cbamber is sligbtly excavate, and 

 tbe sutural lines of tbe segments are often marked out by a tbick 

 secondary sbell growtli. Greatest lengtb of test in tbe specimens 

 from Sinai, | inch (10 mm.) ; diameter at oral extremity, —^ incb 

 (7 mm.) : tbickness, -V inch ('5 mm.). 



Tbe original specimens, described by d'Arcbiac, were from tbe 

 yellow limestone, Hala range, province of Cutcb, India, wbere it 

 was associated vvitb Niimmuliles Bamondi. 0. complanata, var. 

 canalifera, bas also been recorded from tbe nummulitic beds of Beni 

 Hassan and Cairo, Egypt, and from Palestine and Bulgaria. De- 

 scribed under tbe name of 0. lihyca by Scbwager, and recorded by 

 bim from tbe Libyan Series of El-Guss-Abu-Said. 



Coll. Geol. Surv. Egypt, Nos. 4,113 and 4,135, Box Nos. U 

 and 3Z respectively. Libyan Series (Lower Eocene) : junction of 

 Wadi Baba and Wadi Sbellal, Sinai. Abundant and typical. Also 

 No. 3,902, Box No. 15i. Libyan Series (Lower Eocene) : Jebel 

 Krer, Sinai. Frequent, but somewbat dwarfed specimens. 



Operculina complanata (Defrance), var, discoidea, Scbwager. 

 (PL XIV, Fig. 13.) 



Operculina discoidea, Schwager, 1883 : Palaeoutographica, vol. xxx, Pal. Theil, 



p. 145, pi. xxix (vi), figs. ba-d. 

 0. of. canalifera, d'Arch., id., 1883: ibid., p. 144, pi. xxix (vi), figs. 3a, b. 



Tbis variety is distinguisbed from tbe foregoing by tbe even 

 widtb of tbe wborls of tbe sbell, wbicb increase but sligbtly in eacb 

 turn of tbe series. 



