Nomenclature of the Foraminifera. 33 



the still greater potency of the umbilical system of cells is here 

 the sole cause of variation. Many of the globular specimens 

 have an irregular hole or subcylindrical cavity, bevelled off at 

 the margin, on some part of the surface : this is the remnant of 

 the earlier concavity of the base, the edges of which, growing 

 downwards and inwards, have failed to meet and to make up a 

 perfect globe. 



This little spherical Orbitolina, which may be termed O. lavis*, 

 is very common. It occurs also at Fiji, in the West and East 

 Indies, in the Mediterranean, and on the British coast, as far 

 north at least as the Isle of Arran. It is found in the shelly 

 sands of rather shallow water ; whilst the little Orbitolina corru- 

 gata, inhabiting the same seas, lives at a greater depth, on muddy 

 bottoms and in shell-sands. In the fossil state the globular form 

 is found in the Tertiary beds of Palermo, Bordeaux, and San 

 Domingo. The last yields the largest. 



8. Among the spherical specimens from the Rewa reefs of 

 Fiji there are some rather flattened individuals (having the same 

 essential structure as those described above, and ^ inch in dia- 

 meter), which present at their margin one or more small conical 

 or nipple-like processes, composed of cells similar to those of the 

 body, but more compressed. In other specimens these projec- 

 tions are larger and give a lobulate form to the shell, the outline 

 being somewhat like that of an ivy-leaf, and imitating Calcarina 

 Spengleri, or Polystomella unguiculata with thickened spines. 

 Other individuals have subcylindrical spines which do not always 

 lie on one plane. The length of the spine sometimes exceeds. the 

 diameter of the body of the shell. Similar forms occur on the 

 coasts of New Zealand. 



Dr. Carpenter has lately shown us that in these spinous and 

 stellate forms the growth of the shell is symmetrical, the two 

 convex surfaces having about equal proportions of the annular 

 tiers of cells. The vertical section in such forms reminds one 

 of the structure of Orbitoides, excepting, — 1st, that in the latter 

 and flatter Foraminifer the two surfaces of the shell are unequal; 

 2ndly, the over- and under-lying cells have usually an irregu- 

 larity of arrangement ; and 3rdly, the central cells are small, 

 but numerous, regular, and distinct. 



Coexistent with the habit of producing lobes or processes (as 

 holds good also in Calcarina and Polystomella), we find an in- 

 creased development of the interlocular or canalicular passages, 

 to the sarcode of which the granulations and overgrowths in 

 other forms are due. Here we find smooth, minute, glossy 



* On account of the absence of the roughly limbate septal edges seen in 

 some other varieties. 



Ann. $Mag. N. Hist. Ser. 3. Vol vi. 3 



