GENUS TINOPOEUS: — INTEENAL STEUCTUEE. 
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distinct evidence, in sections of this species, of a spiral commencement, soon giving place 
to an irTegularly-cyclical growth ; and sometimes the first-formed portion (Plate XXI. 
fig. 11, «) bears so close a resemblance to the innermost part of the spire of Calcarina, 
that in this earliest stage of their growth the two types could not be distinguished from 
each other. Thus Tinoyorus haculatus seems to bear the same relation to Calcarina^ 
that T. Icevis does (through Planorhulina) to the Rotaline type (^ 217). The essential 
difference between T. haculatus and T. Icevis consists in the possession by the former of 
a “ supplemental skeleton,” which presents itself under two principal aspects. The piles 
of chambers extending vertically from the equatorial plane towards the two surfaces 
of the spheroid (Plate XXI. fig. 7) are partially separated by the interposition of pillars 
of sohd shell (fig. 8, a); and it is by the projection of the summits of these pillars (as 
in Calcarina) that the tubercles of the surface are formed. The spines also, which form 
the extremities of the radiating prolongations, belong to the same system ; and they are 
shown, by sections of the Philippine type that pass in a favourable direction (fig. 6), to be 
extended from a solid framework which begins to be formed even with the first convo- 
lution, and which adds greatly to the thickness of the partitions between the chambers, 
gi\ing off a multitude of minute spines from their external surface (fig. 10, c, c). This 
framework is penetrated by a canal-system, which not only forms passages through the 
solid axis that is prolonged into the spines (fig. 10, a, a), but also extends itself into 
the partitions between the chambers (fig. 9, 5, h). The canal-system of the solid axis, 
moreover, communicates freely with the cavities of the chambers that are adjacent to 
it, as shown at fig. 10, h, h. These chambers are arranged around it with considerable 
regularity, as is shown in fig. 5, which is a transverse section of the base of one of the 
radiating prolongations, showing the solid axis with its radiating canals, surrounded by 
three rows of chambers. It would seem as if, in the Polynesian variety of T. haculatus, 
the material of the supplemental skeleton were appropriated rather to the formation of 
the solid pillars than to that of a solid axis for the radiating prolongations ; the latter 
being much less conspicuous than it is in the Philippine specimens, and sometimes 
appearing to be deficient altogether except at their extremities. On account of the 
variability of these differences, however, I cannot regard them as of any essential 
value. 
222. If any further evidence had been required as to the essential relation between 
the “ canal-system ” and the “ supplemental skeleton,” I think that it must be satisfac- 
torily fui’nished by the comparison of the two species of Tinoporus now described. For 
in T. Icevis it is obvious that the system of communications which exists between its 
chambers is adequate for all the ordinary wants of an organism of this type, the structure 
of which is uniform throughout. But when, as in T. haculatus, an additional framework 
of solid walls is interposed in the midst of the building, for the support of the extensions 
into which it is prolonged, a special system of passages, originating from the cavities of 
the adjacent chambers, and extending throughout the solid framework, is prorided for 
its nutrition. 
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