GENUS CALCAEINA INTEENAL STEUCTUEE. 
of the newest whorl is covered with punctations resembling those of the general surface 
of the disk ; but they are more minute and more closely set together, and they are dis- 
tributed with great uniformity, no unpunctated spaces being anywhere visible. 
202. Internal Structure . — When the internal structure of this organism is examined 
by means of thin sections taken in different directions, the apparent anomalies of its 
conformation are found to be dependent simply upon the extraordinary development of 
its “ supplemental skeleton;” its general plan of structure being much simpler than the 
peculiarities of its aspect would seem to indicate. The spire, as laid open by vertical 
section (Plate XX. fig. 1), is turbinoid ; consisting usually of about five whorls («, a*, 
that start as usual from a central cell, and progressively increase in size, each 
whorl being applied merely to the surface of the preceding, and not investing it in any 
degree, the chambers being altogether destitute of alar prolongations. The aspect of 
the spire as seen in equatorial section is shown in Plate XX. fig. 4 ; this section, being 
taken in such a plane as to cut through the outer whorls passes entirely over 
the surface of the two inner whorls a} and a. The disposition of the chambers, as indi- 
cated by such sections, is ideally shown in Plate XIX. fig. 12. The turns of the spire 
are separated from each other by the interposition of a thick layer of solid shell-sub- 
stance ; and this is quite distinct from the proper walls of the chambers, as may be well 
seen in Plate XX. fig. 4, where the walls of the newest chambers are shown at h to be 
entirely destitute of any such addition, whilst at in the preceding part of the same 
whorl we observe them encrusted by a thin additional layer c?, and, as we trace this layer 
backwards to I and d, we perceive that it progressively augments in thickness, until it 
acquires its maximum at d, just where it is covered by the subsequent whorl. This 
distinction between the proper walls of the chambers and the “ supplemental skeleton ” 
can be traced to the very centre of the spire. The septa are entirely formed by the 
infolding of the proper walls of the chambers, which are there flattened against each 
other so as to form two layers, which are usually in contact, but which sometimes 
diverge (especially near the external margin of the chambers) to give passage to canals. 
There does not appear, however, to be any regular “ interseptal system ” as in O'per- 
culina and Polystomella. The communication between the adjacent chambers of the 
same whorl is effected, as in Polystomella, through series of pores (fig. 1, c) disposed at 
pretty regular intervals along the inner margin of the septum*. 
203. That the spines entirely originate from, and are strictly appendages of, the 
“ supplemental skeleton ” is well seen in fig. 4, which shows their connexion with its 
* Messrs. Paekee and Joxes say (Ann. of Nat. Hist. Ser. 3. vol. v. p. 175) of the aperture of Calcarina, 
that “ in well-preseryed specimens of the typical forms, the real aperture, which is essentially a slit, as in the 
true Botalice, becomes bridged over by delicate bars of shell-matter.” I cannot but think that they have 
allowed themselves in this statement to be somewhat influenced by a foregone conclusion that “ Calcarina 
is a subgenus of Jtotalia'' The examination of numerous sections of the character represented in fig. 5 
leaves no doubt in my own mind that the aperture of Calcarina is essentially such as I have above described ; 
and that if it occasionally in perfect specimens has the character of a continuous fissure (which I woMd by 
no means take upon myself to deny), such is an aberrant rather than the ordinary form. 
MDCCCLX. 4 D 
