FORAMINIFERA OF THE NORTH PACIFIC OCEAN. 35 



Genus AMPHISTEGINA d'Orbigny, 1826. 



Amphistegina d'Orbigny (type, A. lessonii d'Orbigny) Ann. Sci. Nat., vol. 7, 

 1826, p. 304.— H. B. Brady, Rep. Voy. Challenger, Zoology, vol. 9, 1884, 

 p. 739. 



Description. — Test spiral, lenticular, more convex on one side than 

 the other, the last-formed volution usually covering the others, cham- 

 bers with the alar projections on one side simple, divided on the 

 other side by deep constrictions to form supplementary lobes; wall 

 thickened near the umbilicus, usually smooth except near the aper- 

 ture on the ventral side where it is usually papillose, no true secondary 

 canal system developed; aperture on the ventral side at the base of 

 the chamber, simple. 



There are various forms of this genus but by the foregoing charac- 

 ters they may be distinguished. Occasionally there is some surface 

 ornamentation but usually the wall is smooth. It is often very 

 abundant in the shallow waters of the Tropics. 



AMPHISTEGINA LESSONII d'Orbigny. 



Plate 19, fig. 2. 



Amphistegina lessonii d'Orbigny, Ann. Sci. Nat., vol. 7, 1826, p. 304, No. 3, 

 pi. 17, figs. 1-4; Modeles, No. 98. — Parker, Jones, and H. B. Brady, Ann. 

 Mag. Nat. Hist., ser. 3, vol. 16, 1865, p. 34, pi. 3, fig. 92.— H. B. Brady, 

 Rep. Voy. Challenger, Zoology, vol. 9, 1884, p. 740, pi. Ill, figs. 1-7.— H. B. 

 Brady, Parker, and Jones, Trans. Zool. Soc, vol. 12, 1888, p. 230, pi. 43, 

 fig. 15. — Egger, Abh. icon. bay. Akad. Wiss. Munchen, CI. n, vol. 18, 1893, 

 p. 431, pi. 20, figs. 18, 19.— Flint, Ann. Rep. U. S. Nat. Mus., 1897 (1899), 

 p. 338, pi. 82, fig. 4. — Fornasini, Rend. Accad. Sci. 1st. Bologna, vol. 7, 

 1903, pi. 2, fig. 1.— Sherlock, Bull. Mus. Comp. Zool., vol. 38, 1903, p. 356, 

 fig. 5. — Millett, Journ. Roy. Micr. Soc, 1904, p. 605. — Bagg, Proc. U. S. 

 Nat. Mus., vol. 34, 1908, p. 165. — Chapman, Proc. Roy. Soc. Victoria, vol. 22, 

 pt. 2, 1910, p. 294, pi. 53, fig. 6. 



Description. — Test lenticular or more convex on one side than the 

 other, surface smooth, composed of about 25 chambers in the last- 

 formed volution which embraces the preceding ones, chambers on 

 the dorsal side with the alar projections simple, on the ventral side 

 divided by deep constrictions usually into two lobes, especially in the 

 thicker varieties the test is papillose about the ventral margin of the 

 aperture, aperture Eotaliform, simple. 



Diameter up to 3 mm. 



Distribution. — Brady does not record this species from the Chal- 

 lenger material of the North Pacific. Bagg records it from eleven 

 Albatross stations in the vicinity of the Hawaiian Islands, depths 

 ranging from 104 to 1,544 fathoms. 



Among the various lots of material I have had this species was 

 very common in that from Gaspar Straits, from Cagayan, Philippines, 

 collected by Dr. E. A. Mearns, Alert station 1177 in 23-118 fathoms 



