34 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
to the north shore of Cuba, between Cardenas and Nuevitas, its present 
configuration. Only in the case of Florida a greater stretch of the land 
to the rear of the keys was changed into flats and bars than is the case 
on the Cuban coast. (See Pl. XIII. Figs. 1-4, Bull. Mus. Comp. Zoöl., 
XXVI. No. 1.) 
The corals of the elevated. reef on Elliott Key belong to the safne species 
as those occurring on the patehes of the elevated reef of Indian Key, of 
Lower Matecumbe, and of Key Largo. They are mainly species of Orbi- 
cella, Astrea, Mieandrina, and Colpophyllia. On Elliott Key many large 
patches of the reef rock consisted entirely of the shells of conchs. 
The Ship Channel, separating the outer line of reef patches from the 
main line of keys, may represent a sink of greater extension, which the 
currents have swept clean, and gradually deepened after it became freely 
connected with the sea at many points and along wide stretches. Here 
and there only do we find in the channel reef patches, the remnant of 
larger patches of the former elevated reef, upon which corals are now 
growing. Such patcbes are the Middle Ground, the Hen and Chickens, 
Washerwoman East and West Shoals, the North Shoals, the Triangles, 
and the innumerable bars aud heads which fill the channel east of Carys- 
fort Reef back of Ajax Reef, and stretch towards Fowey Rocks, where 
the outer reef almost joins the inner line of keys. 
The seaward extension of the elevated reef and reef flats and patches 
can be traced along the outer line of the reof from Sand Key to the east- 
ward, as well as along the line of heads which stud the Ship Channel. 
The Hen and Chickens heads are formed by corals growing upon 
patches of the older elevated reef, which can be seen rising irregularly 
from various depths. The faces of these patches all show the effect of 
the action of the sea, and are cavernous and deeply eroded. We found 
that the Fowey Rocks, as well as the ledges near them, showed the 
same structure; but both at the Fowey Rocks and at Alligator Reef 
Madrepora palmata plays an important part in the growth of the corals 
covering the heads, while in the Hawks Channel the heads are mainly 
Gorgonians, Orbicellas, Micandrinas, Astreans, and coralline Algee, with 
comparatively few Millepores. In the Florida district the slight de- 
velopment of Millepores is in marked contrast with their abundance 
in the Bahamas and Bermudas. On Plantation Key the elevated reef 
rises to a height of nearly fifteen feet. 
An examination of the heads of the Washerwoman Shoals shows very 
plainly the old decomposed reef rock forming the base upon which the 
new heads of the existing reef have grown. Тһе heads are surrounded 
