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 Rotalice, and which, in certain Asterigerine varieties 

 (such as Asterigerina lobat a, D ; 'Orb. — a variety oiRotalia Beccarii, 

 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 y 1 ^ 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 a slight 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 0. vesicularis has much resemblance to some of the 

 Planorbulinee ; but the latter have two or three tubular and margined 

 apertures to each chamber, they have coarser pseudopodial pores, and 

 no umbilical cells. 



