36 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 
reef north of Fowey Rocks, to the disconnected patches west of Alli- 
gator Reef as far as Sand Key, and to the open line of keys stretching 
west of Key West to the Marquesas. 
The outer reefs are growing upon old reef rock ledges, now elevated. 
They flourish on the ruins of the old roof, which itself must be under- 
lain by the shore extension of the formation known as tho Pourtalés 
Plateau. This near the outer edge of the reef is covered with sand 
and reef material, so that its in-shore limit cannot be determined except 
by borings. According to Mr. Hovey's determination, the thickness of 
the elevated reef at Key West is probably not greater than fifty feet. 
It now becomes an interesting question to trace on the mainland the 
inner limits of the elevated reef. What we know of the subject we owe 
to the observations of Professor L. Agassiz and Professor Shaler, but 
they only penetrated a comparatively short distance inland from the 
shore of Key Biscayne. To obtain additional information on this point, 
Mr. L. S. Griswold made, at my request, an expedition into the interior, 
with the intention of reaching Long Key on the edge of the Everglades, 
and of ascertaining the nature of the rock which is said to crop to the 
surface at that part of the Everglades. 
Mr. Griswold succeeded in reaching a point close to the so called 
Long Key," and gives a most interesting account of the appearance of the 
southern part of the Everglades. He penetrated inland a distance of 
about twenty-three miles, He ran three lines into the interior, one from 
Black Point Creek, at the western extremity of Key Biscayne Bay, a 
second line following the Miami River and branching off in a westerly 
direction towards Long Key, and a third line following the course of 
New River. He also explored Florida Bay as far as Cape Sable to the 
east, and extended his observations to the north along the east coast of 
Florida, examining such localities as Boca Ratones, Lake Worth, Linton, 
and Cape Canaveral. 
Mr. Griswold traced the extension of the molian limestones more or 
less modified to the most distant point he reached, though he consid- 
ers the oólitie rocks he collected as having been formed under water, 
an opinion with which I cannot agree. The specimens he has col- 
lected aro all, in my opinion, only modified molian rocks, such as are 
found anywhere in the Bahamas and Bermudas. The very odlitic bluff 
to the westward of Miami River, 
a photograph of which I owe to him 
(Plate XIX.), — which in his opinion has been deposited in water, is 
a most characteristic wolian rock, showing in its stratification the 
1 See his route, Plate XVII. 
