On the Ginathodon beds around the head of Mobile Bay. 167 
_ It is evident however that new masses of shells are still form- 
ing in the beds of these streams, in every respect similar to those 
which are found in elevated situations. These submerged beds 
also illustrate the method by which the others have been amassed 
to such a remarkable extent. The living part of the species are 
frequently liable to perish in becoming too deeply imbedded by 
‘ an unusual increase of alluvium, a very common event in this 
ic delta region ; the continued propagation of the species in such 
circumstances, admits of the continued increase of the mass to 
an indefinite extent. Superficial marsh-deposits are of no rare 
occurrence in the vicinity in which the shells are thinly scattered 
was the way of their formation. It is not improbable that those 
elevated masses which occur free from such earthy mixture, 
existed originally in a similar mixed state, the drifting of the cur- 
rent, or the drenching of the rain, having divested the deposits of 
the more moveable earthy portion of their ingredients. 
The partially submerged state of the next class of deposits, 
be s 
unmixed shells in a submerged state along the shore. Or finall 
when the mass was elevated, some individuals may have contin- 
ned to live and multiply by the shore, forming an apparent con- 
Unuation of the original deposit. 
The Submerged portion of these beds may often be traced to 
a distance of man rods. They occur principally in insular 
and marshy situations, remote from the main land; particularly 
ton, and was since intersected by numerous rivers and creeks, as 
of Water fowls, alligators, &c.; and last though not least, of im- 
mense quantities of molluses, the accumulated masses of whose 
remains are scattered at short intervals over the entire extent of 
this region. 
_ The third class of beds consists of those. which are wholly 
elevated above the water; they are principally situated on the 
Main land, near the first terrace from the water’s edge, at nearly 
, pi: elevations above the tide. They are usually of an oblong 
ape, their longest axis being parallel with the neighboring 
