30 Messrs. W. K. Parker and T. R. Jones on the 
2. In the Indian seas is a similar little shell (about >45 inch 
in diameter), which, however, exhibits four narrow curved cham- 
bers (each forming nearly three-fourths of a circle), arranged 
around a central, globular primordial cell, and composing the 
low cone of the shell and its thin margin. In company with 
this (which represents a varietal stage in advance of No. 1), we 
find other specimens (about ,/, inch in diameter) possessing as 
many as ten semiannular chambers. This variety may be termed 
Orbitolina semiannularis. 
8. From the Arctic, British, Mediterranean, and other seas we 
have obtained some specimens of a very small Foraminifer (4, inch 
diameter) having the shape of the one last described, and a very 
similar arrangement of chambers. It has, however, a greater 
complexity of structure, owing to the presence of numerous 
secondary septa, transverse and short, in all but the first two or 
three chambers. These superadded septa begin to appear in a 
rudimentary form in the third or fourth chamber, on the inside 
of the peripheral wall; they never reach the umbilical border 
of the annulus, and are irregular in their development, even in 
the newest chambers, where they are sometimes thirty or more 
in number. The base of the shell, or umbilical area, is traversed 
by raised, sinuous, thread-like lines of shell-matter. In older 
individuals these are succeeded by thicker and irregularly wavy 
ridges, and ultimately nearly the whole of the basal surface is 
masked by this exogenous growth, excepting a thin margin, 
formed by the newest of the annular chambers, the transverse 
septal lines of which are also limbate by superadded calcareous 
matter. 
This shell, in its different stages of growth, has been well 
described and illustrated, under the name of Patellina corrugata, 
by Prof. Williamson (Monograph, p. 46, pl. 3. figs. 86-89) ; and 
he notices the difficulty of placing this shell in its true relation 
to other forms. 
Orbitolina (Patellina) corrugata is present in most sea-beds 
that are rich with Foraminifers, from the littoral zone down to 
500 fathoms; but it does not occur in great abundance. 
4. In the shore-sands from Melbourne, Australia, rich with a — 
group of Foraminifers almost the exact counterpart of those of 
Grignon, we find a small, subconical, finely perforated shell, 
exceedingly like that last noticed (No. 3), but not unfrequently 
attaining four times the size (4, inch). A difference, however, 
exists. After the primordial chamber, there is usually only one 
semilunar chamber, those succeeding being annular. The latter 
are subdivided by short, transverse secondary septa, as in 0. 
corrugata; and the cells have a regular alternately concentric 
arrangement. 
