534 Transactions of the Society. 



sistiug of three distinct series of chambers arranged in one plane 

 representing three distinct life-periods, of each of which we have 

 been fortunate enough to secure perfect and typical examples. 

 These three life-periods are as follows : — 



1. An initial series of seven or eight chambers arranged in one 

 plane in a compressed and evolute spiral, all the chambers being 

 visible on both faces of the test. The chambers grow rapidly in 

 thickness, so that a young shell at the period of the completion of 

 this first or " Discorbine " stage of growth is somewhat wedge- 

 shaped in vertical section. 



2. An intermediate or " Pavonine" stage, consisting of two or 

 three chambers, which, rapidly increasing in width (as opposed to 

 depth, which from the completion of the first or Discorbine stage 

 remains pretty constant during the remaining growth), overlap and 

 infold the initial or Discorbine series. 



3. A final series of narrow annular chambers arranged concen- 

 trically round the earlier stages. 



The completed test is usually symmetrical and roughly circular 

 in outline, but is sometimes more or less irregular both in outline 

 and in superficial appearance, as though it had grown in contact 

 with an irregular surface. No attached specimens have, however, 

 been found as yet. 



The test is distinctly and somewhat coarsely perforated. As 

 the test increases in growth and age, the walls become thickened 

 by a deposit of shell substance between the tubuli, and the surface 

 then assumes a rough, or areolated appearance, distinctly visible in 

 balsam mounts, due to the cup -shaped depressions left round the 

 perforations (plate XII. fig. 7). The edges of these cups appear to 

 have been produced into minute spines, which are especially notice- 

 able round the perforations on the oral faces of the chambers, where 

 they have been included and protected from injury by the growth 

 of the succeeding chambers (plate XII. fig. 6). 



The continual deposition of this shell-substance causes the older 

 shells to assume a crenulate, or even warty, superficial appearance, 

 which masks the sutural lines. The plan of growth then becomes 

 very obscure, but is still readily observable in balsam mounts. 



Aperture. — There is no special oral aperture in any of the 

 stages of growth. The only communication between the successive 

 chambers consists of the ordinary tubuli, which are equally dis- 

 tributed over the septal face of the chambers, as well as over the 

 outer sides. The septal tubuli do not differ in any way from the 

 other perforations. 



This absence of special aperture is one of the most marked 

 features of the genus, and has no parallel in the perforate Forami- 

 nifera outside the Tinoporina?, of which sub-family the absence 

 of a special aperture is a characteristic feature. 



The genus Cycloloculina will be placed in the second sub-family 



