50 



labours 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, snperadded 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. 



Madrepora diver gens 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 musicalis, described by Ellis* and by Borlase-f, which 

 is said to be formed chiefly in the Indian Ocean, and frequently thrown 

 in large masses oh 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. 

 f Borlase's Cornwall. P. 241. Plate XXVII. Fig. 7. 



