rORAMINIFERA OF THE ATLANTIC OCEAN. 

 Cristellaria latifrons — material examined. 



127 



Genus MARGINULINA D'Orbigny, 1826. 



Marginulina D'Okbigny (type, M. gladra D'Orbigny), Ann. Sci. Nat., vol. 7, 

 1S26, p. 258.— H. B. Brady, Rep. Voy. Challenger, Zoology, vol. 9, 1884, p. 

 526.— Chapman, The Foraminifera, 1902, p. 191.— Cushman, Bull. 71, U. S. 

 Nat. Mus., pt. 3, 1913, p. 79. 



Description. — Test subcylindrical, early portion close-coiled, later 

 chambers uncoiled, rounded in transverse section, the last-formed 

 chambers often inflated; aperture in early chambers marginal, later 

 often becoming nearly median, usually radiate. 



It is a question whether the species placed under this genus might 

 not be included under the uncoiled Cristellarias. In general the 

 chambers of the uncoiled portion in Marginulina are nearly circular 

 in transverse section and the ornamentation is usually limited to 

 longitudinal costae. 



Its geological history goes back, as does that of Cristellaria and 

 Nodosama^ to the Cambrian. 



MARGINULINA GLABRA D'Orbigny. 



Plate 36, figs. 5, 6. 



Marginulina glabra D'Orbigny, Ann. Sci. Nat, vol. 7, 1826, p. 259, No. 6; 

 Modeles, No. 55. — Parker, Jones, and H. B. Brady, Ann. Mag. Nat. 

 Hist., ser. 3, vol. 16, 1865, p. 27, pi. 1, fig. 36.— H. B. Brady, Proc. 

 Somerset Arch, and Nat. Hist. Soc, vol. 13, 1867, p. 109, pi. 2, fig. 22.— 

 Balkwill and Wright, Proc. Roy. Irish Acad., ser. 2, vol. 3, 1882, 

 p. 548.— H. B. Brady, Rep. Voy. Challenger, Zoology, vol. 9, 1884, p. 

 527, pi. 65, figs. 5, 6. — Balkvpiix and Wright, Trans. Roy. Irish Acad., 

 vol. 28, 1885, p. 344, pi. 12, figs. 24, 25.— H. B. Brady, Journ. Roy. 

 Micr. Soc, 1887, p. 910. — Pearcey, Trans. Glasgow, Nat. Hist. Soc, 

 vol. 2, 1890, p. 178. — Wright, Proc. Roy. Irish Acad., ser. 3, vol. 1, 

 1891, p. 485. — Robertson, Proc. Nat. Hist. Soc. Glasgov?, pt. 3, 1892, 

 p. 241.— Heron-Allen and Earland, Proc Roy. Irish Acad., vol. 31, 

 pt. 64, 1913, p. 97; Trans. Linn. Soc London, ser. 2, vol. 11, 1916, 

 p. 261. 



Description. — Test elongate, tapering, cylindrical in transverse 

 section ; chambers in the early portion coiled, later portion uniserial, 

 uncoiled, the last formed chamber fairly elongate, tapering to the 



