REPORT ON THE EORAMINIFERA. 
743 
The larger and more characteristic varieties of Operculina are abundant in the tropical 
and sub-tropical seas of the eastern hemisphere, generally at depths of less than 30 
fathoms, but also from time to time in deeper water. The smaller, starved variety 
inhabits a much wider area, its northern limit extending considerably within the arctic 
circle, but it is comparatively seldom met with south of the equator. 
Cornuel has described a fossil, to all appearance a true Operculina, 1 from the Lower 
Cretaceous (Neocomian) beds of Haute-Marne, and Eeuss has figured two forms, evidently 
Operculince, from the chalk of Maestrickt ; 2 but the genus is comparatively rare prior to 
the commencement of the Tertiary epoch ; it is found abundantly, however, in the lime- 
stones of the Nummulitic period and in many subsequent formations. 
Operculina complanata, Defrance, sp. (PI. CXII. figs. 3, 4, 5, 8). 
“Operculum minimum,” Plancus, 1739, Conch. Min., p. 18, pi. iii. fig. 1, a.b.c. 
Lenticulites complanata, Defrance, 1822, Diet. Sci. Nat., vol. xxv. p. 453. 
,, ,, Basterot, 1825, Mem. Geol. Env. Bordeaux, pt. i. p. 18. 
Operculina complanata , d’Orbigny, 1826, Ann. Sci. Nat., vol. vii. p. 281, pi. xiv. figs. 7-10; — 
Modele, No. 80. 
,, ammonea, Leymerie, 1846, Mdm. Soc. geol. France, s6r. 2, voh i. p. 359, pi. xiii. 
fig. 11, a.b. 
„ complanata, Rutimeyer, 1850, Schweizer Nummuliten-terrain, p. 108, pi. iv. 
fig. 56. 
,, arabica, Carter, 1853, Journ. Bombay Br. R. Asiatic Soc., vol. iv. p. 437, pi. xviii. 
,, liardiei, d’Archiac and Haime, 1853, Descr. Anim. Foss, du groupe nummulitkpie de 
l’lnde, p. 346, pi. xxxv. fig. 6, a.b.c. 
„ complanata, Parker and Jones, 1861, Ann. and Mag. Nat. Hist., ser. 3, vol. viii. 
p. 229. 
,, studeri, Kaufmann, 1867, Geol. Beschreib. des Pilatus, p. 151, pi. ix. figs. 1, 2. 
„ marginata, Id. Ibid. p. 152, pi. ix. fig. 4. 
,, complanata, Moebius, 1880, Foram. von Mauritius, p. 104. 
Operculina complanata, var. granulosa, Leymerie (PI. CXII. figs. 6, 7, 9, 10). 
Amphistegina fleuriausi, d’Orbigny, 1826, Ann. Sci. Nat., vol. vii. p. 304, No. 7 (name only), 
fide Reuss. 
Operculina granulosa, Leymerie, 1846, Mdm. Soc. g<$ol. France, sdr. 2, vol. i. p. 359, pi. xiii. 
fig. 12, a.b. 
Amphistegina fleuriausi , Reuss, 1861, Sitzungsb. d. k. Ak. Wiss. Wien, vol. xliv. p. 308, pi. i. 
figs. 10-12. 
Operadina irregularis , Reuss, 1864, Denkscbr. d. k. Akad. Wiss. Wien, vol. xxiii. p. 10, pi. i. 
figs. 17, 18. 
„ granulata, Gumbel, 1868, Abbandl. d. k. bayer. Akad. d. Wiss., II. Cl., vol. x. p. 663. 
pi. ii. fig. Ill, a.b. 
1 Operculina angularis, Cornuel, 1848, MJm. Soc. gdol. France, ser. 2, vol. iii. M<bn. III. p. 256, pi. ii. figs. 20-22. 
2 Operculina cretacea, Reuss, 1861, Sitzungsb. d. k. Ak. Wiss. Wien, vol. xliv. p. 309, pi. ii. fig. 1 ; and the so- 
called Amphistegina fleuriausi. 
