390 
MR. W. K. PARKER AND PROFESSOR T. R. JONES ON SOME 
Genus Pulvinulina. 
Pulvinulina repanda , Fichtel and Moll, sp. (Varieties). Plate XIV. figs. 12-17 (Arctic); 
Plate XVI. figs. 35-51 (North Atlantic). 
Pulvinulina repanda is the type of a group of Botalince, as above mentioned (page 378), 
of which we have here five varieties. Each of these belongs to a separate subspecific 
group ; and, though they are few among many, yet they are of considerable importance 
in their several sub-groups, and may well serve as a basis for a general account of Pul- 
vinulina repanda specifically considered. 
P. repanda , when well developed, has its shell-structure dense and minutely perfo- 
rated, compared with that of other Potalinm ; more so than Potalia Beccarii and Calca- 
rina Spengleri , and much more so than Piscorbina Turbo and Planorbulina farcta. In 
the delicacy of its tubuli (almost as fine as those of dentine) it rivals Nummulina and 
Heterostegina ; whilst the loose coarse structure of some of the larger specimens of Pis- 
corbina and Planorbulina remind us of that of the Echinoderm and Madrepore. 
Pulvinulina is most apt to take on an extra growth of shell-matter on the septal lines 
and the margins of the shell (limbation), and among its very numerous varieties there 
are many that are strongly limbate, and are more or less compact in growth ; whilst other 
varieties are delicate, and become thin, outspread, Spirilline, and vermiculate. The 
shell has from seven to nearly thirty cells, with single septa and but little trace of the 
canal-system : it is rarely prickly ; the umbilicus is often ornamented by granules, or by 
a boss, or a star of shelly matter ; the aperture is a large fissure, often arched, and 
notched ; and the septal face often bears numerous coarse subsidiary perforations. The 
shell is usually biconvex ; the upper side the thickest ; the margin more or less angular 
and subcarinate ; some varieties are complanate, with square edges, as in Roemer’s figures 
of P. caracolla and its allies from the ITils Clay and the Gault ; similar forms to these 
occur also in the Kimmeridge Clay of Kimmeridge. 
We may divide the Pulvinulinoe into five groups, as follows: — 
First Group, or that including P. repanda proper. — In its typical form P. repanda is a 
spiral coil of chambers, forming a low conical shell, showing the spire, with a more or 
less open umbilicus ; some of the older chambers usually having limbate septa. The 
shell has generally an irregularly oblong form ; the chambers rarely forming a symme- 
trical disk, never flush at the edges, but set on loosely, and usually increasing in size in 
a somewhat rapid ratio ; they present often a curved or sickle-shaped outline both above 
and below, or are curved and narrow above, broad and irregularly triangular below. 
The umbilical portions of the chambers are generally very attenuate, fitting neatly as 
they converge to the centre. Occasionally these lobes are separated by narrow chinks ; 
sometimes they are deficient, leaving a large umbilical gap. The septal face is either 
gently convex, or flat ; in the latter case it is perforated with proportionally large holes. 
The aperture is a large arched slit, occasionally notched at its upper margin. Granulate 
ornament is not uncommon on the upper surface of the shell ; below, exogenous matter 
