32 DE. CAEPENTEE’S EESEAECHES ON THE EOEAIHINIEEEA. 
meter of the recent specimens does not elsewhere exceed -065 inch, it attains m some of 
the Philippine examples as much as -115 inch, thus equalling that of the largest fossil 
specimens which have come under my notice. The general con'ectness of Professor 
Williamson’s description of this species I can fully confirm ; hut the companson of a 
large number of sections leads me to the unhesitating conclusion that the inequilateralit}- 
which has been considered the distinctive character of this type is so inconstant, as to 
forbid our assigning any value to it as a generic, still less as an ordinal character. It is 
often very strongly marked in the fossil AmpUsteginm of the Vienna and St. Domingo 
tertiaries ; but it is as frequently absent altogether, the shell being perfectly equilateral ; 
and between these two extremes of form we find every intermediate gradation. ^ So it 
frequently presents itself among the small specimens of Anvphistegina giblosa which are 
common in tropical seas, and I have met with specimens exhibiting as great a want of 
symmetry as the one of which Professor Williamson has delineated a section ; yet on 
the whole, I should say, that in the great bulk of the smaller specimens which ha^e 
passed under my notice, the want of symmetry is but slight ; whilst perfect equilateraHty 
both of external form and of internal arrangement not unfrequently occurs ; and in those 
large specimens from the Philippines which present this type in its highest development, 
there is little or no departure from exact symmetry. — But further, Mr. Cuming s collection 
furnishes numerous examples of a remarkable species whose general conformity of 
structure to AmpUstegina gihhosa seems to leave no doubt of its near relationship to it 
(the resemblance of its younger specimens to that specific type being so close as to have 
led me in the first instance to a belief in the specific identity of the two), and yet the 
most exact symmetry here presents itself as the rule, departures from it being excep- 
tional, and never proceeding to any considerable extent. It may be considered, there- 
fore, Is satisfactorily established, that want of lateral symmetry is not to be held as an 
essential character of the shells of this genus, although more frequently occurring in it 
than in Nummulites or Operculina, to which, as I shall now show, this type bears an 
extremely close relationship. 
167. The species to which I have just referred being hitherto undescribed, I shall 
designate it A. Cumingii. In its young state it is lenticular in form (Plate V. figs. 13, 14), 
and is only distinguishable from the symmetrical variety of A. giUosa by the smaller 
number and greater angular distance of the septal bands which radiate from the centie 
and suddenly turn backwards as they approach the margin. (The radiating portions of 
these septal bands, as will presently appear, mark the direction of the portions of the 
septa that intervene between the alar prolongations of the chambers ; whilst the lecur- 
rent portions mark the direction of the portions of septa that separate the principal 
cavities of the chambers.) As the A. Cumingii advances in life, however, a marked 
change presents itself in its form, corresponding to that which I have shown to occur in 
Heterostegina, Peneroplis, and Operculina’, for the spire, after about its fourth turn, 
begins to flatten itself out, and separates itself henceforth from the central portion of 
the shell, to which it affords a very partial investment (figs. 15-17), the spiral lamina 
