TROPICAL PACIFIC FORAMINIFERA OF "ALBATROSS" 57 



Test similar to Operculina, the early chambers simple, later ones 

 divided into chamberlets; aperture consisting of a row of rounded 

 openings on the narrow apertural face. Eocene to Recent. 



The same remarks already made imder Operculina will apply almost 

 equally well to this genus, although the range of variation does not 

 seem to be so great, and the specimens fall more easily into a few 

 distinct groups. It is rather striking that so many of the species are 

 from Albatross stations, which may indicate that Heterostegina curva 

 at least is represented in fairly deep v/ater. There is always the 

 possibility, however, that these may have been carried out by currents 

 or wave action, and represent specimens which have been filled with 

 air on dried beaches, and therefore float for some time until they are 

 again picked up by waves. 



HETEROSTEGINA DEPRESSA d'Orbigny 



Plate 16, Figures 4-9 



Heterostegina depressa d'Orbigny, Ann. Sci. Nat., vol. 7, p. 305, no. 2, pi. 17, 

 figs. 5-7, 1826; Modeles no. 99, 1826.— Parker, Jones, and H. B. Brady, 

 Ann. Mag. Nat. Hist., ser. 3, vol. 16, p. 34, pi. 3, fig. 100, 1865.— H. B. Brady, 

 Rep. Voy. Challenger, Zoology, vol. 9, p. 746, pi. 112, figs. 14-20, 1884.— 

 Egger, Abh. kon. bay. Akad. Wiss. Miinchen, CI. ii, vol. 18, p. 433, pi. 20, 

 figs. 34, 35, 1893. — Chapman, Joiirn. Linn. Soc. Zool., vol. 28, p. 18, pi. 3, 

 figs. 6, 7, 1900. — MiLLETT, Journ. Roy. Micr. Soc, 1904, p. 606. — Rhumsler, 

 Zool. Jahrb., Abt. Syst., vol. 24, p. 74, 1906. — Cushman, U. S. Nat. Mus, 

 Bull. 71, pt. 4, p. 38, pi. 19, fig. 5, 1914. — Chapman, Biol. Results Endeavour. 

 vol. 3, pt. 1, p. 33, 1915. — Heron-Allen and Earland, Trans. Zool. Soc. 

 London, vol. 20, p. 738, 1915. — Cushman, Carnegie Inst. Washington 

 Publ. 213, p. 289, 1918.— Heron-Allen and Earland, Journ. Linn. Soc. 

 Zool., vol. 35, p. 641, 1924. — -Yabe and Hanzawa, Sci. Rep. Tohoku Imp. 

 Univ., ser. 2 (GeoL), vol. 14, p. 43, pi. 2, fig. 4; pi. 13, fig. 7 (part), 1930. 



Test complanate, the early portion usually somewhat involute and 

 thickened, later portion very thin and flaring, early chambers only 

 slightly divided, becoming increasingly so in the later ones, periphery 

 thin and rounded with a slight specialized border such as is frequent 

 in this and the preceding genus; chambers elongate, curved, numer- 

 ous, divided into chamberlets by transverse partitions usually alter- 

 nating in adjacent chambers, the division into chamberlets first 

 appearing on the periphery and progressivelj^ working farther and 

 farther in toward the central portion as growth progresses; sutures 

 distinct, slightly limbate, not raised but occasionally very slightly 

 depressed in the adult, strongly curved, often somewhat sigmoid; 

 aperture at the base of the final chamber together with a series of 

 pores along the apertural face. Length, up to 2.5 mm; breadth, 

 1.85 mm; thickness, 0.35 mm. 



This species has been recorded from numerous localities particularly 

 in the Indo-Pacific. It is found at only a few stations in our material, 



