60 t Dr Forch hammer on the 



bles much some specimens of chalk-like limestone from under 

 the basalts at the Giant's Causeway in Ireland. The most re- 

 markable phenomenon this limestone offers is the complete 

 difference of its petrifactions from those of the chalk, and the 

 close analogy which they bear to those of the calcaire grossier, 

 although they are perhaps not the same species. Although it 

 is only about a year since I discovered this bed, yet a consi- 

 derable number of fossils have been found ; and no doubt 

 it will furnish a great number, since every observer that visited 

 the cliff and paid some attention to this bed has discovered 

 some new ones. I will give here an enumeration of those ge- 

 nera which I observed partly myself, and partly owe to the 

 kindness of my friend Mr William Lund. 



One species of Patella ; one species of Cyprea ; one species 

 of Fusus ; two species of Cerithium ; one species of Ampul- 

 laria ; one species of Trochus, (the Trochilites Niloticifbrmis 

 of Schlotheim ;) one species of Serpula ; one species of Den- 

 talium; one species of Area; one species of Mytilus ; one 

 species of Spatangus ; one species of Favosites ; one species 

 of Turbinolia ; the teeth of fishes; besides several univalves 

 and bivalves and corals, of which the genus is not determin- 

 able, on account of their bad state of preservation. 



The limestone in some places is full of small round green 

 grains. This bed seldom exceeds three feet in thickness ; now 

 and then it is only a few inches, but nowhere it seems entire- 

 ly wanting. By its fossils, its green particles, and its great 

 external difference from the chalk, it seems to be analogous to 

 the calcaire grossier of the vicinity of Paris. Its proper po- 

 sition upon the chalk is on the whole cliff everywhere evident, 

 and no real chalk is found again above it ; but it is covered by 

 a limestone, which is almost entirely composed of fragments of 

 broken corals. 



The coral limestone forms in many places the uppermost 

 part of the cliff, and has a thickness of thirty or forty feet. 

 By beds of corneous flint it is divided into a number of sub- 

 ordinate beds. But the regularity which was so striking in 

 the real chalk, the parallelism of the subordinate beds, has en- 

 tirely disappeared. The beds of flint are constantly bent, and 

 in whatever direction the cliff may show its sections, the beds 



