50 
labour of each colony seems to have been protracted, so that the per- 
pendicular fibres were extended in a waving form, by which the fossil ob- 
tains somewhat of a foliaceous appearance, as appears from the sketch 
in outline, superadded to the above figure. This sketch, so illustrative 
of the mode in which the little animals extend their habitations, is taken 
from a drawing of the Rev. Joseph Townsend, being a faithful repre- 
sentation of the superior part of a specimen in his possession. 
Madrepora organum formed by smooth cylindrical tubes about the 
size of wheat-straw, combined together at a little distance from each 
other by somewhat waving membranes, is figured in Fig .VI. No. 1, of 
Corallia Baltica. This coral is said to be found in a recent state in the 
Red Sea ; but it is much more frequently found in a fossil state, chiefly 
on the shores of the Baltic. r 
Madrepora divergens is a fossil coral, much like to, and, perhaps, 
only a variety of, the coral just treated of ; but of neither of these can 
I speak from my own observation. 
Madrepora mmicalis, described by Ellis* and by Borlase,*j- which 
is said to be formed chiefly in the Indian Ocean, and frequently thrown 
in large masses on the shores of Ireland, has not to my knowledge 
been seen in a fossil state. 
Madrepora denticulata and mad. rotulosa are very unlikely to be 
detected in a fossil state, from the delicate structure of the elevated 
lamellae at their edges being so very liable to injury, by the attrition 
to which substances which have become mineralized have generally 
been exposed. 
Madrepora faveolata, I have reason to suppose, is sometimes seen in 
a mineralized state. But the specimen which I refer to this species, 
having been cut at both its upper and lower surfaces from a large 
specimen, I am unable to speak decidedly respecting it. Indeed in 
fossils of this genus, the cavities are generally so filled up as to prevent 
* Philosophical Transactions. Vol. LIII. P. 432. 
t Borlase’s Cornwall. P. 241. Plate XXVII. Fig. 7. 
