292 F. CHAPMAN. 
Operculina complanata, Defrance sp., Newton and Holland, 
1902, Journ. Coll. Sci., Imp. Univ. Tokyo, Vol. xvi, 
Art. 6, p. 13, pl. i, figs. 3, 5; pl. iii, fig. 3. Chapman, 
1908, Proc. Linn. Soc. N.S. Wales, Vol. xxxu, pt. iv, 
p. 749, pl. xxxvii, figs. 1, 2; pl. xxxviii, fig. 3. 
Several tests of the above species occur in the limestone 
sections; but the form is not so common as that of Hetero- 
stegina depressa in the same rock, and which it much 
resembles in section. In Heterostegina the area around 
the umbilical axis in vertical section is correspondingly — 
thicker than in Operculina, and a few fragments in hori- 
zontal section bear out this determination. 
O. complanata is a typical and common form in almost 
all Cainozoic deposits laid down in warm temperate seas. 
Amongst other places it occurs at Muddy Oreek, Victoria 
(Oliogocene), and the New Hebrides (Miocene); as well as 
in the Raised Coral Reefs of the Loo Choo Islands, Japan 
(? Pleistocene). 
Genus HETEROSTHGINA, d’Orbigny. 
HETEROSTEGINA DEPRESSA, d’Orbigny. Plate IX, fig. 9. 
Heterostegina depressa, d’Orbigny, 1826, Ann. Sci. Nat., 
Vol. vil, p. 305, pl. xvii, figs. 5-7; Modeéle, No. 99. 
Brady, 1884, Rep. Chall., Vol. 1x, p. 746, pl. cxii, figs. 
14-20. Chapman, 1900, Journ. Linn. Soc. Lond. Zool., 
Vol. xxviii, p. 18, pl. iii, figs. 6, 7. 
Unlike the structure of the living forms of this species, 
which show in the majority of cases that they belong to 
the megalospheric stage (propagation by budding), the 
Papuan fossil examples are nearly always microspheric 
(adapted for sexual generation). 
H. depressa is very common in thin slices of the Papuan 
limestone. The species is widely distributed, generally in 
coral seas and warm temperate areas, and is found fossil 
from Hocene times. . 
