Nomenclature of the Foraminifera. 31 
The annularity of the chambers in this larger variety is a 
marked parallel to the concentric cyclical growth of Orbitolites, 
small delicate varieties of which have frequently no annular 
chambers, whilst the large forms are almost wholly cyclical. 
The under surface of this Australian Patelline Orbitolina 
(which we denominate O. annularis) is concave, partially occupied 
by superadded imperfect cells, entangled, as it were, in the exo- 
genous matter, which tends to arrange itself in granules, and 
more or less obscures the annular structure, which is still, how- 
ever, apparent towards the margin. The rudimentary cells in 
the umbilical shell-substance are evidently homologous with 
those secondary lobes which are formed on the umbilical surface 
of certain Rotalig, and which, in certain Asterigerine varieties 
(such as Asterigerina lobata, D’Orb.—a variety of Rotalia Beccarit, 
Linn.), attain a well-marked and symmetrical development. 
5. In the white mud of the coral-reefs of Australia, at from 
10 to 20 fathoms, there is an abundance of a still larger form, 
with a diameter of ;4, inch and upwards, retaining the same 
essential characters of structure as the foregoing, but presenting 
a modification of the secondary chambers, the annular chambers 
being divided into numerous small vesicular cells. Here the 
vesicularity gradually masks the annularity of the structure, 
until, except sometimes in the thinnest specimens, we have a 
massive little cellular body, sometimes resembling a delicate 
Planorbulina, sometimes losing itself in a low cone of thickly set 
minute vesicles. . 
In these specimens the secondary or cross septa of the annular 
chambers are perfectly developed, compared with the short abor- 
tive partitions in O. corrugata; and the exogenous umbilical cells 
of the variety No. 4 (from Melbourne) have been advanced to the 
condition of cells almost as large and perfect as those of the sub- 
divided annuli. The umbilicus is so far filled up that the base 
of the cone is almost flat, although generally the last two annular 
series of chambers may be seen from beneath (as in the case of 
O. corrugata), and aslight concavity remains. This is our variety 
O. vesicularis. 
As the subdivisions of the annular chambers lose the cuboidal 
form and become vesicular, they take on a polygonal shape, being 
placed alternately concentric. The shell also has the pseudopodial 
passages relatively larger than in the less-developed forms with 
flattened feeble cells*. Thus also in delicate conical varieties of 
Rotalia Turbo (such as R. rosacea, D’Orb., and Asterigerina 
* In this state O. vesicularis has much resemblance to some of the 
Planorbuline ; but the latter have two or three tubular and margined 
apertures to. each chamber, they have coarser pseudopodial pores, and 
no umbilical cells. 
