CHOANITES. 
107 
which penetrate the substance, and terminate in 
openings on the inner surface ; central cavity, 
cylindrical, deep, narrow ; base fixed by radical 
processes. 
a. Choanitis Konigi. 
h. Section of the same. 
This species is for the most part enveloped in 
large irregular flints, which exhibit but slight 
traces externally, of the body they enclose. The 
superior part {a) presents a convex surface, with 
a cylindrical body in the centre, from whence in- 
terrupted fibres, slightly relieved, ramify in a 
radiating manner towards the margin. At the 
base, numerous perforations are seen, through 
which the radical processes pass. The vertical 
section (Z>) exposes the cylindrical cavity filled 
with flint, and the substance of the zoophyte tra- 
versed by numerous tubes ; some of which appear 
to terminate on the outer, and others on the inner 
surface. In chalk specimens, this structure is also 
very distinctly displayed, and on the surface are 
markings as if of cruciform spines, like those with 
which some recent alcyonia are furnished. 
