554 
DE. CAEPENTEE’S EESEAECHES OX THE EOEA^nXITEEA. 
successive convolutions. Thus the spine e is one of the oldest, being traceable inwards 
to the earlier whorls ; whilst those marked are obviously of progressively 
later production, their respective origins being further and further removed from the 
centre of the spire. It is, moreover, to be observ^ed that each spine receives an augmen- 
tation in thickness as the convolution from which it sprang is encircled by others ; this 
augmentation, however, is not marked (as in the spines of Echini) by lines of demai’ca- 
tion between the earlier and the later formations ; and there is every reason to beheve 
that the growth of the spines, both in length and in diameter, is continuous rather than 
interi’upted. Although it might seem, fr’om the examination of such sections only as 
are taken in the direction of the equatorial plane or in one parallel to it, as if the coui'se 
of the spire must be seriously interrupted by the radiation of the spines (which some- 
times appear to be so interposed between consecutive chambers as completely to separate 
them) ; yet the fact is that owing to the turbinoid form of the spfre, a spine projecting 
from an earlier whorl is very little in the way of even the next convolution ; for as this 
passes by the spine on a different level, its chambers are but slightly encroached-on, and 
this only upon the side which looks towards the apex of the spire, — as will be readily 
understood by examining the relation of the last half-convolution, ■sisible in such a 
specimen as the one delineated in Plate XIX. fig. 4, to the pre-formed spines, or by an 
inspection of the ideal represented in Plate XIX. fig. 12. 
204. The canal-system of Calcarina presents a development so extraordinary in itself, 
and so obviously related to that of the “ supplemental skeleton,” as to throw great light 
upon its special functional destination. We do not here observe any such peculiar but 
limited distribution of systematically arranged passages, as that which constitutes so 
remarkable a feature in Eolystomella ; but every portion of the supplemental skeleton, 
with the exception of certain solid cones presently to be noticed, is traversed by canals 
which run very close together, with frequent inosculations, and which thus form a con- 
tinuous network with long narrow meshes, that commences from the parietes of the 
chambers and extends itself to the very extremities of the spines (Plate XX. figs. 1, 2, 4). 
The proper walls of the chambers, as afready stated, are uniformly perforated, like those 
of the chambers of Eotalioe^ by foramina of considerable size (averaging about 
of an inch in diameter) ; with these the canals of the supplemental skeleton do not 
seem to be directly continuous, for they are of about double the diameter and lie 
further apart from one another; but immediately round the proper walls of the 
chambers (as shown in Plate XX. fig. 1) there seem to be iiTegular lacunar spaces, 
into which their foramina open externally, and from which the passages of the 
canal-system originate. How numerous and closely-set these passages are, is shown 
in Plate XX. fig. 3, which is taken (under a much higher magnifying power than 
the rest of the figures) from a section that passes through the supplemental skeleton 
just outside the walls of one of the chambers, in such a direction as to cut through 
the passages transversely or obliquely. These passages run in different dfrections; 
some proceeding directly towards the external margin of the convolution, and being 
