REPORT ON THE FORAMINIFERA. 
619 
Sphceroidina, d’Orbigny. 
Sphceroidina, d’Orbigny [1826], Rronn, Reuss, Ehrenberg, Costa, Egger, Parker and Jones, 
Karrer, Seguenza, Carpenter, Scbwager, Ponrtales, M. Sars, Hantken, Brady, &c. 
Sexloculina, Czjzek [1847]. 
Grammobotrys, pars, Ehrenberg [1854]. 
Globigerina, pars, Schwager [1866]. 
Bolbodium, Ehrenberg [1873]. 
The genus Sphceroidina was originally described by d’Orbigny in the “ Tableau 
Methodique,” and a place was assigned to it at the end of the Family Eyallostegia, 
immediately following Virgulina. The author subsequently found reason to alter his 
opinion, and in the “ Vienna Basin” memoir it appears amongst the Agathistegia, between 
the Milioline genera Triloculina and Quinquelocidina. Prof. Beuss, in his classification 
of the Foraminifera, published in 1861, gives it a position in his Family Polymorphinidea, 
between Robertina and Dimorphina. 
The near relationship of the genus to Globigerina was first suggested by Dr. Carpenter 
and his colleagues; and their view, as propounded in the Introduction to the Study of the 
Foraminifera, is supported not merely by structural analogy, but by many facts which 
have since been ascertained in connection with the distribution of the two recognised species. 
The diversity of opinion which has existed as to the affinity of the genus is mainly due to 
the somewhat obscure external characters of the test, and the slight indication they afford 
of its internal structure. 
The test of Sphceroidina is globular or subglobular in contour, and consists of a small 
number of extremely convex segments, arranged as a short spire. Owing to the 
embracing character of the chambers and their rapid increase in size, only the final 
convolution, which is generally composed of three or four segments, is visible externally. 
Sometimes, however, by a slight obliquity, or one-sided development of the spire, a larger 
number of chambers are discernible, but even in such cases the plan of growth is not 
always apparent. The texture of the shell and its condition with respect to perforation 
are variable features. The aperture is an arched or nearly semicircular opening, often 
partially closed by a shelly tongue so as to form a crescentic fissure, and is situated close 
to the inner margin of the final segment. 
The geographical distribution of Sphceroidina is almost world-wide. It is found at 
every latitude from the middle of the west coast of Norway to the shores of Prince 
Edward Island in the Southern Ocean; and its bathymetrical range includes every depth 
from 30 fathoms to 2600 fathoms. The genus has a pelagic representative in Sphceroidina 
dehiscens, which is a frequent constituent of the surface-fauna of micl-ocean. The earliest 
appearance of Sphceroidina, geologically speaking, is in the Cretaceous period, but it does 
not become common or widely diffused until the middle of the Tertiary epoch. It is of 
frequent occurrence in marine deposits of Miocene and Pliocene age. 
