REPORT ON THE FORAMINIFERA. 
683 
Pulvinulina partschiana represent only the extreme development in two opposite direc- 
tions of an unbroken series of which that species occupies the central position. The 
sequence of minute morphological changes which the series reveals has been indicated 
with more or less detail by the authors already referred to ; and, though the Challenger 
collections contribute not a little to our knowledge of the subject, it is scarcely needful 
to repeat with greater minuteness what has already been clearly and effectively stated. 1 
With few exceptions, the shells of the Pulvinulince are constructed on the Rotaliform 
plan, but they assume every variety of contour, from the conical, with flat inferior 
face ( Pulvinulina procera), to the reverse condition, in which the superior face is flat and 
the inferior convex or conical ( Pulvinulina mickeliniana) ; the intermediate forms being 
more or less biconvex ( Pulvinulina repanda). A few of the weaker modifications become 
evolute and present a thin outspread shell ( Pulvinulina pauperata). The shape of the 
test is further diversified by the greater or less rapidity of the progressive increase of the 
size of the chambers, which determines its relatively circular ( Pidvinidina harsteni ) or 
oblong {Pulvinulina auricula ) peripheral outline. The umbilicus is either closed by 
the meeting of the inner margins of the chambers {Pulvinulina repanda)], or deeply sunk 
{Pulvimdina mickeliniana), or the cavity is filled up with exogenous deposit {Pidvinidina 
elegans). The shell- wall is very finely porous, the tubulation being more minute and 
delicate than in any of the allied Rotaline genera. The septal walls .are always single, 
and there is no evidence of even a rudimentary canal system. The exterior of the test is 
usually smooth ; occasionally it is hispid, granular, or rugose, or beset with raised beads 
or tubercles ; but for the most part any exogenous deposit takes the form of external 
thickening or limbation of the sutures and chamber-margins, especially on the inferior 
side of the test. 
Parker and Jones divide the genus into a number of subordinate groups, based chiefly 
upon the relative prominence and degree of development of the various features above 
enumerated, taking into account also the bathymetric range of the constituent species. 
The five divisions they propose are typified by Pidvinidina repanda, Pulvinulina 
auricula, Pulvinulina menardii, Pulvinulina schreibersii, and Pulvinulina elegans 
respectively. The details of the classification are open to some objections, but on the 
whole it affords as convenient a framework as can be devised for the arrangement of a 
long and otherwise unmanageable series of forms. According to this scheme, the recent 
species described in the present Report are apportioned as follows : — The depths, which 
are quoted from Parker and Jones's synopsis, require considerable revision. 
I. “ The type or repanda group ; 10-100 fathoms.” 
Pulvinulina repanda, P. concamerata, P. punctidata, P. concentrica, 
P. vermiculata, and P. dispansa. 
1 Parker and Jones, Phil. Trans., vol. civ. p. 390. — Carpenter, Introd. Foram., p. 210. 
