34 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



to the north shore of Cuba, between Cardenas and Nuevitas, its pi-esent 

 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 PI. XIII. Figs. 1-4, Bull. VI us. Comp. Zool., 

 XXVI. No. 1.) 



The corals of the elevated reef on Elliott Key belong to the same species 

 as those occurring on the patches of the elevated reef of Indian Key, of 

 Lower Matecumbe, and of Key Largo. They are mainly species of Orbi- 

 cella, Astnea, Mseandrina, 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 patches are the Middle Ground, the Hen and Chickens, 

 Washerwoman East and V»*est Shoals, the North Shoals, the Triangles, 

 and the innumerable bars and heads which fill the channel east of Carys- 

 forfe Pieef 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 reef 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 Mocks 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, Maeandrinas, Astrseans, and coralline Alga?, 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 

 bo 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. The heads are surrounded 



