REPORT OR THE EORAMINIFERA. 
681 
favourable circumstances, the segmentation of the first convolution may be distinctly 
traced (fig. 8). There are usually about five segments in each convolution ; they are 
convex or inflated externally, and the sutures are strongly marked. In large specimens 
it frequently happens that the inner margins of the segments of the terminal whorl do 
not meet, but leave a deep umbilical hollow, as seen in figs. 6 and 9. The aperture is an 
arched slit at the inner edge of the final chamber, at or near the line of union with the 
previous convolution. The walls are thick, and, except near the base of the test, coarsely 
perforated. The length of adult specimens is sometimes j^th inch (1*68 mm.), or even more. 
It is obvious that, from a morphological point of view, the base of the test corresponds 
with the superior or spiral face of the typical Rotalian shell, the successive whorls being 
added vertically, that is to say, on the summit of those previously formed, instead of 
laterally, at the circumference. 
The foregoing description is drawn from well-grown typical specimens, of which the 
series figured in PI. XCVIII. furnishes good examples. But the species presents consider- 
able range of variation, and a large proportion of the specimens from some localities have 
the opaque shells and comparatively obscure external characters delineated in the original 
drawings ; and this is often accompanied by defective segmentation. Occasionally the 
shell is incrusted with extraneous bodies, such as sand, sponge-spicules, and the like — a not 
uncommon feature in some of the Planorbuline genera ; and sometimes the mouth is 
crowded with sponge-spicules, as frequently seen in Polytrema and Carp criteria. 
Rupertia stabilis has its home in the northern portion of the North Atlantic. A few 
scattered examples have been found in the southern hemisphere, but it has never been 
taken within the tropics, nor indeed wdthin about 35° north or south of the equator. The 
figured specimens are all from a single point in the “cold area” of the Faroe Channel, 
depth 632 fathoms, where the species exists in extraordinary abundance. Those 
collected by Dr. Wallich were from “ three soundings taken on opposite sides of the 
southern extremity of Greenland — the depth in the three localities varying from 108 
fathoms on the east coast, to 1205 fathoms on the west.” The species occurs at thirteen 
“ Porcupine ” Stations and one Challenger Station in the North Atlantic, — the latter, off 
the Azores, being the most southerly — the depth ranging from 5 fathoms on the Rockall 
Bank, to 1360 fathoms. Poor examples have been met with in dredgings from off the 
Cape of Good Hope, 150 fathoms, north of the Falkland Islands, 1035 fathoms, and in 
the South Pacific, near Juan Fernandez, 1375 fathoms. Schlumberger’s specimens were 
from the Bay of Biscay. 
Pulvinulina, Parker and Jones. 
Nautilus, pars, Soldani [1780], Fichtel and Moll. 
Serpula, pars, Montagu [1808]. 
Cidarollus, Eponides, Cancris, Montfort [1808]. 
Pulvinulus, pars, Lamarck [1816]. 
