26 BULLETIN 104, UNITED STATES NATIONAL MUSEUM 



sutures often slightly limbate; the walls coarsely punctate, on the 

 dorsal side irregularly so, the punctae near the outer margin of the 

 chamber, less frequent elsewhere; aperture an elongate, slightly 

 arched slit at the inferior margin of the chamber; color white. 



Diameter up to 0.65 mm. 



This is a common species in the West Indian region in shoal water. 

 It is beautifully ornamented and is not likely to be mistaken for 

 any other Discorbis of the western Atlantic. The young has a 

 brownish color which is lost in the thickened adult test. It occurs 

 fossil in the Miocene, Choctawhatchee marl of Florida. 



The species is probably widely distributed in the Pacific like many 

 of the West Indian species, and is probably recorded as "Discorbina 

 turbo" following Brady's identification in the Challenger Report. 



Brady's Challenger figures are of specimens from the Cape Verde 

 Islands. He also records it from Bermuda and off the coast of 

 Brazil. I have had it from numerous West Indian localities. 



DISCORBIS NITIDA (Williamson) 



Plate 6, figures 1 a-c 



Rotalina nitida Williamson, Rec. Foram. Gt. Britain, 1858, p. 54, pi. 4, 

 figs. 106-108. 



Rotalia niiida H. B. Brady, Trans. Linn. Soc. ZooL, vol. 24, 1864, p. 474; 

 Nat. Hist. Trans. Northumberland and Durham, vol. 1, 1865 (1867), 

 p. 105. — Balkwill and Wright, Trans. Roy. Irish Acad., vol. 28, Sci., 

 1885, p. 352.^ — Siddall, Proc. Lit. Philos. Soc. Liverpool, 1886, p. 71. — 

 Halkyard, Trans. Manchester Micr. Soc, 1889, p. 71, pi. 2, fig. 12. — 

 MiLLETT, Rec. Foram. Galway, 1908, p. 7. 



Discorbina mtida Wright, Ann. Mag. Nat. Hist., ser. 6, vol. 4, 1889, p. 

 449; Proc. Roy. Irish Acad., ser. 3, vol. 1, 1891, p. 490. — Chaster, First 

 Rep't. Southport Soc. Nat. Sci., 1890-91 (1892), p. 65.— Wright, Irish 

 Nat., vol. 9, 1900, p. 55. — Heron-Allen and Earland, Proc. Roy. Irish 

 Acad., vol 31, pt. 64, 1913, p. 121; Trans. Linn. Soc. London, ser. 2, 

 vol. 11, 1916, p. 269, pi. 42, figs. 26-30; Journ. Roy. Micr. Soc, 1916, 

 p. 49; 1930, p. 182. 



Test plano-convex, making a low nearly symmetrical cone in side 

 view, periphery subacute, mth a narrow keel; chambers very dis- 

 tinct but not inflated, usually five or six in the last-formed whorl, 

 very gradually and regularly increasing in size as added; sutures 

 distinct, thickened on the dorsal side due to the keel of the chamber, 

 strongly curved on the dorsal side, but not depressed, ventrally 

 radial, slightly depressed; wall smooth throughout, very finely 

 perforate; aperture at the base of the chamber near the umbilicus; 

 color usually bluish-white. 



Diameter up to 0.50 mm.; height of spine 0.15 mm. 



This is a characteristic species of the European coast of the Atlantic, 

 well figured by Williamson in 1858. Our figured specimen is from off 



