(40) 
stone and clay-slate mix with and alternate with each 
other, previously to their entire separation, and te 
their taking their regular and respective courses. 
Madreporites seem not to be confined to any par- 
ticular spot, but are discoverable in almost every part 
of the stratum of Limestone, from the Dock-Yard 
to the Flying Bridge. In some places, they are not 
so distinctly visible, from the circumstance of “their 
being but thinly scattered in the stone, and from 
their not having been exposed to the action of the 
weather ; while in others, they lie in families, con- 
sisting of large masses, and forming extensive layers ; 
as in the Quarry at Mill-Bay; at Sandy Cove; in 
the rocks of the East Hoe, nearly under the Cita- 
del; and in Dead Man’s Bay, near Catdown. 
Univalve and Bivalve Shells, wherever they occur, 
{ have never found mixed together, but always in 
separate beds. Thus, for instance, the Shells of the 
Dock-Yard, Mount Wise, and the North side of 
Stonehouse Hill, are all Bivalves; while those from 
the South side of Stonehouse Hill, from the rocks 
at the end of the East Hoe, under the Citadel; and 
