KAEAKOEAM STONES, OE SYEINGOSPHA^EIDA]. 
16 
and environed by broader interradial series, with slightly larger, closer, and very bent tubes. 
The tubes of the radial series are wider apart than the others, although their course is usually 
radial and straight; they often bend much here and there, are irregular, and are often genicu¬ 
late at the sides. They unite by means of very small offshoots, and bifurcate, but rarely 
increase in number sufficiently to present the aspect of a cone in the mass. They rather 
form linear radial lines. 
The larger and closer interradial series bend, unite, bifurcate, and are singularly gyrose, 
varicose, and irregular in their course in many places. They are often so close together that 
they resemble knots of tubes, and then the section having cut across many, exhibits the 
more or less circular incision in the tube-wall and the lumen. 
The tubes are usually diameter, those of the interradial series being the 
largest. Throughout the number of tubes in the interradial series is very great. 
In some spots calcite has filled up a vacant space which was evidently once a surface 
pore, and in one or two places the tubes end at one of these places. New tubes were formed 
distally to the space by the arching over of side ones, and the branches taking a radial 
direction. In some parts the radial tubes are smaller than in others, and then there is 
manifest difference between them and those of the adjoining interradial series, which branch 
ffive off offshoots from one side, and twist in a close and remarkable manner. 
o 
The interspaces between the radial tubes are the largest, and those of the interradials are 
very minute. 
Towards the centre of the section a confused mass of convoluted tubes exists, and the 
radial and interradial series appear to start from it. The tubes are thin at the wall, and the 
structural element, granular, molecular and thinly set, is minute in the extreme. 
At the surface of the body every granule with its circlet of pores is the outlet of a 
radial series, and the space between the granules, pores included, represents the interradial 
structure within. 
The greatest breadth of the spheroidal body is one and a half inch. 
Syeingosph^eia poeosa, Duncan. Plate II, Pigs 3, 4. 
The body is very oblately spheroidal in shape and symmetrical. The surface is covered 
with minute low, rounded granules. The granules vary much in size, the pores are exceedingly 
numerous and unequally distributed, and the space between many of them is in ridges, 
giving a boldly reticulate appearance, especially equatorially. No large amount of tube 
reticulation is visible on the surface; on the contrary, it appears, except at the pores, to be 
made up of tubes opening directly with circular or oblique outlines, and of wide intertubular 
interspaces filled with dark calcite. Where there is much space between the pores, the 
irregularity of this calcite indicates the former existence of peripheral tubes which have 
weathered out; but where the granules show any structure, it is that of tubes on their sides, 
converging upwards and opening at the top, and of tubes opening on the centre of the top. 
The pores are clearly spaces where tube-growth has not progressed equally with that of the 
surrounding parts. The sides of the pores present tubes passing radially, and tubes open on 
their floor. 
Tangential sections, under low powers, exhibit localised and more or less circular groups 
of tubes which correspond to granules. In some the tubulation is reticulate, and in others, so 
radial that only the cut ends of tubes are seen. There are spots where the reticulation is 
