on the Geology of East Florida. 39 
Bivalves. Cardium magnum. 
Ostrea virginiana. Lucina diyaricata. 
Pinna ————.* Petricola dactylus. 
Mytilus edulis. 
itus Say. Univalves.. 
Tellina lateralis, Say. Ranella caudata, Say, 
Amphidesma equalis, Say. Crytostoma perspectiva, Say. 
Mactra lateralis, Say. Crepidula plana, Say. ' 
Solecurtus caribeus. Littorina irrorata, Say. 
Arca pexata, Say. Oliva litterata. 
A. incongrua, Say. Fulgur carica 
A. ponderosa, Say. F. canaliculata. 
Donax variabilis, Say. Natica duplicata ? 
All of these, except Fulgur carica and Solecurtus caribeus, 1 
found subsequently at Tampa bay. 
About half a mile from the river, I observed sand hillocks cov- 
ered with bleached oyster shells, among which I found some spe- 
cimens of Arca perata, and a water worm Gnathodon. truncatus. 
This is a marine Post-pliocene deposit, which corresponds with 
the estuary bed of Ostrea virginiana alluded to as occuring in the 
bank of St. Johns river. The living Gnathodon I was unable 
to find here, and I am persuaded does not exist in this part of 
Florida. ; 
One of our officers landing at Fort Lauderdate, found a speci- 
men of Tellina radiata. 1 presume this is about the northern 
limits of this beautiful but common bivalve. _. 
Having landed at Key Biscayne to take in water, I had. time 
for ashort walk, during which I observed myriads of the Polygyra 
Plicata, Say, in most places near the beach. seirc 
On Indian Key I was first made acquainted with the geological 
Structure of this chain of small islands, which border the eastern 
and southern coast of the Florida peninsula. This island con- 
tains only eleven acres, and is composed of a Post-pliocene lime- 
Stone, which in places seems little more than a cement for myriads 
of shells of such species as live in the waters of this latitude, 
and which are generally identical with those of Cuba. The rock 
on many parts of the shore is hard and full of large cavities, 
which are lined with four species of Nerita,t and myriads of Lit- 
torina muricata traverse the bare rocks far above the limit of 
Oe ee ee ee : 
* A spinous species common in Tampa bay. : 
t W. peloronta, N. tessellata, N. versicolor, and N. pica. 
