8 BULLETIN 161, UNITED STATES NATIONAL MUSEUM 



opposite the middle of the chamber but sometimes at the angle; 

 chambers distinct, slightly inflated, of uniform shape and increasing 

 only slightly in size as added, few in number, usually 5 to 7 in the 

 adult coil, those of the earlier coils often showing through the clear 

 umbilical region; sutures distinct, strongly limbate, nearly straight 

 and tangential; wall smooth, very finely perforate; aperture somewhat 

 projecting, radiate, with a ventral slit along the middle of the apertural 

 face, which is slightly depressed and has raised sides. Diameter 

 without spines, usually about 1 mm or less. 



Forms similar to that figured here are not uncommon in many 

 parts of the world in the present oceans and in the late Tertiary. 

 References are very numerous to this species, but only a few that 

 refer to typical material are given here. Specimens are only in the 

 deep-water material of the Albatross dredgings, and even there seem 

 to be extremely rare, occurring only at H3961, center south coast of 

 Tarawa, 10 miles N., in 413 fathoms. 



ROBULUS EXPANSUS (Cushman) var. PLANULATUS (Cushman) 



Plate 2, Figures 4a, b 



Cristellaria expansa Cushman var. planulata Cushman, Proc. U. S. Nat. Mus., 

 vol. 51, p. 658, 1917; U. S. Nat. Mus. BuU. 100, vol. 4, p. 237, pi. 46, figs. 

 3a, b, 1921. 



Variety differing from the typical form mainly in the lack of the 

 characteristic ornamentation, which consists of raised beads, and 

 in the variety if at all ornamented, consisting of indistinct costae 

 in the axis of growth; the test is also more compressed than in the 

 typical form. 



This variety was originally described from the Philippines, and is 

 present in the Albatross dredgings in typical form from a single station, 

 H3924, Nukutipipi Atoll, 1 mile NW., in 649 fathoms. 



Genus MARGINULINA d'Orbigny, 1826 



Marginulina d'Orbigny, Ann. Sci. Nat., vol. 7, p. 258, 1826. 



Genotype. — By designation, Marginulina glabra d'Orbigny. 



Test subcylindrical, very early portion close coiled, later uncoiled, 

 final chambers often inflated; aperture in the early coiled portion as 

 in Lenticulina, in the uncoiled portion becoming central and terminal. 

 Triassic to Recent. 



A distinction is sometimes attempted between the more rounded 

 and flattened uncoiled forms usually assigned to Marginulina, with 

 the name Hemicristellaria Stache applied to those forms that are 

 flattened. There is no possibility of drawing a dividing line between 

 these forms, and moreover the designated type of Hemicristellaria, H. 

 procera Stache, is not a compressed but a rounded form, as a study of 



