110 Papers from the Marine Biological Laboratory at Tortiigas. 



THE HAWK CHANNEL. 

 ^ Behind the keys is an open-water channel, known as Hawk Channel, 

 having shoals from place to place in it and extending from the upper 

 end of the series of reefs to the Marquesas. Its maximum depth is from 

 5.5 to 6 fathoms, and its width varies from 3 to 7 miles. The landward 

 boundary is formed by the main line of keys. 



THE KEYS. 



The Florida Keys are a series of islands rising sHghtlv, a maximum 

 of 10 to 12 feet above tide-level, forming a curve paralleling the reefs, 

 bounded by the landward side of the Hawk Channel as far as the Marque- 



FiG. I. — Tortugas, East Ke)-, west side looking north. Note vegetation 

 on the summit of the kev. 



Fig. 2. — Middle Key looking north along the axis. This key was washed 

 away during a storm on June 28, 1909, but was restored between 

 August, 1909, and May, 1910. 



sas, and extending from the seaward face of Biscayne Bay to the Tortu- 

 gas. In form these keys may be divided into three groups; 



(i) The first group consists of long, narrow islands, stretching 

 along a gentle curve to the southwest from Biscayne Bay to Bahia 



