108 
formed, that they ought to be seen for any one to geta 
just idea of them*: but te proceed with the description as 
well as Imay. It is very compact, with a partly con- 
choidal and somewhat splintery fracture, and more or less 
composed of fibres radiating from the axis with an inclination 
towards the ends of the branches, without any sign of the 
usual rhomboidal fracture of Carbonate of Lime. This texture 
continues throughout the whole formation, whether globu- 
Jar, curving, branching, or inosculating. The centre is 
generally most dense and opaque, and the outside opens 
into spiculee—see the right hand figure ;—other fresh spi- 
cule seem to be emerged as it were, and form a covering. 
Sometimes the outward spiculz are very transparent, giving 
a velvety appearance in particular lights. Sometimes there 
are small grains of the equiaxed form of common Carbonate 
of Lime upon the surface, giving it a curious appearance— 
see the lower left hand figure. 
Its gravity and hardness help to distinguish it. Probably 
its density may answer for these characters, as it effervesces 
with acids, and is dissolved very readily, like other Car- 
bonates of Lime. The variety figured on the last plate will 
often form one specimen with this. 
* Mr, Sowerby will most willingly show them to his friends, on the first 
or third Tuesday in the succeeding months of the year. 
