52 
nodules, but is evidently disposed between all the branches : and even 
the spathose matter which has filled the cavities of the coral has received 
a strong red tinge from the oxide of iron. A polished section of this 
stone manifests this, and shews that if it could be obtained in masses 
sufficiently large, it might, from the closeness of its texture, be employed 
for many useful purposes. It is indeed a marble of rather dull appear- 
ance ; but it would not be without its beauties, since the little variety 
of colouring which it possesses is pleasingly disposed, and would be 
somewhat enlivened by the stellated spots yielded by the transverse 
sections of the coral. 
Madrepora fascicularis, a figure of which is given in Silesia Subterranea 
V olkmanni. Tab. XVII. Fig. 14, is a fossil w'hich possesses a very 
distinguishing character ; the tubes of which it is formed almost always 
shewing, in their longitudinal section, numerous transverse septa, as 
may seen in the small specimen, Plate VI. Fig. 11. This peculiar 
appearance results from the following structure of this coral. It is 
formed of slightly diverging, cylindrical tubes, which are so closely 
beset by transverse septa, as scarcely to leave, sometimes, a space of 
the sixteenth of an inch between them. The stars of this madrepore 
are composed of about thirty radii or perpendicular lamellae ; half of 
which reach, from the circumference, to about one-third of the semi- 
diameter from the centre, while the other scarcely extend one-third of 
the semidiameter from the circumference. Hence the centre of the 
tubes, for one-third of their diameter, are perfectly free from any 
perpendicular laminae ; in the next space of one-third, these perpendi- 
cular laminae are but thinly placed ; and it is only in the space next 
the sides of the tubes that these laminae are fully disposed. In 
consequence of this arrangement it is obvious, that a perpendicular 
section, through nearly the centre of the coral, must in general display 
the transverse septa only ; since in every longitudinal section they 
must be divided and exposed, whilst the longitudinal lamellae must 
necessarily be partly concealed, even if the tubes are not filled with 
