REPOET ON THE FORAMINIFERA. 
535 
Cristellaria italica, and in other cases acutely angular or carinate, as in Cristellaria 
variabilis. 
The aperture is either terminal and marginal, or situated in the peripheral angle of 
the final segment. It consists sometimes of a circular opening with the rim divided by 
radiating fissures ; sometimes of a simple orifice, either round, oval, angular, or slitdike, 
with or without a radiate corona of embossed or depressed lines. D’Orbigny’s division of 
the group into two genera, Cristellaria and Robulina, was based solely on the nature of 
the orifice, whether rounded or slit-shaped, a feature altogether too uncertain and variable 
to be of any service to the systematist. 
The immediate allies of Cristellaria are Vaginulina and Marginulina. No hard lines 
of demarcation can be drawn between the three generic groups ; but, broadly speaking, 
it may be said that Cristellaria differs from Vaginulina in the invariably spiral 
arrangement of the earlier chambers, and from Marginulina in its compressed contour — 
Vaginulina being typically entirely non-spiral, and Marginulina having rounded or sub- 
cylindrical segments. 
The genus is distributed over an area stretching from the Arctic seas, lat. 79° 45' N., 
to Magellans Strait, lat. 52° 50' S. It inhabits all the great oceans, the Red Sea, the 
Mediterranean, and the Adriatic. Its bathymetrical range embraces every depth from the 
littoral zone to nearly 3000 fathoms, but it attains its best development on bottoms of 
from 50 to 50.0 fathoms. 
The earliest appearance of fossil Cristellarice is in the Upper Trias; 1 they are abundant 
in the Lias, and from that geological period down to Post-tertiary times they are met 
with in marine deposits of almost every age. 
Cristellaria tenuis, Bornemann, sp. (PI. LX VI. figs. 21-23). 
Marginulina tenuis, Bornemann, 1855, Zeitschr. d. deutsch. geol. Gesellscli., vol. vii. p. 326, 
pi. xiii. fig. 14. 
Cristellaria perprocera, Schwager, 1866, Novara-Exped., geol. Theil, vol. ii. p. 241, pi. vi. fig. 84. 
,, tenuis, Reuss, 1870, Sitzungsb. d. k. Ak. Wiss. Wien, vol. lxii. p. 479, No. 1. 
,, legumen, Seguenza, 1880, Mem. R. Accad. dei Lincei, ser. 3, vol. vi. p. 141, pi. xiii. 
fig. 12. 
This is one of the attenuated, linear group of Cristellarice, the spiral segments of 
which are few and inconspicuous, and the normal contour of the shell compressed as in 
Vaginulina. Not unfrequently, however, the later segments are subcylindrical or 
inflated, like those of the Dentaline varieties of Nodosaria. The Marginulina ensis of 
Reuss (Haidinger’s Naturw. Abhandl., vol. iv. p. 27, pi. ii. fig. 16), is a very similar 
form, but the test is subcylindrical throughout. 
1 Very recent observations place the first appearance of the genus as far back as the Lower Silurian. See footnote, 
p. 548. 
