AGASSIZ: BAHAMAS. 105 



miles off in a southeasterly direction. The entrance is steep to directly 

 soutli of Northwest Cay, while a long sunken spit extends from South 

 Cay to the northwest, encroaching upon neai'ly half the opening to the 

 lagoon. Coral heads are scattered all the way across the entrance, in 

 six to nine fiithoms of water; they become quite abundant and luxuriant 

 as we approach the Northwest Cay, and are continued in sliallower water 

 on the outer rim of the atoll all the way to the eastern face, seemingly 

 finer and more thriving as they extend to the eastward. 



The same is the case with the heads on the outer face of the southern 

 and eastern face of the atoll; the coral heads increase in size and num- 

 ber as they extend towards the eastern extremity, and take their fullest 

 development on the comparatively broad shelf stretching to the eastward. 

 As far as I could ascertain with the water glass and lead the coral heads 

 do not extend beyond eighteen or nineteen fathoms, but owing to 'the 

 steepness of the outer slope of the atoll it was difficult to decide this. 

 When we examined the eastern shelf the sea was too rough to enable me 

 to detect the presence of heads beyond seventeen fathoms, and at that 

 depth they were more distant, and frequently separated by large patches 

 of coral sand, while towards the atoll they gradually became more nu- 

 merous and more thickly crowded, attaining apparently their maximum 

 of development in the belt inside of ten fathoms. 



The poverty of the coral fauna of the interior of the lagoon is very 

 striking. As I have stated above, the bottom is nearly level, sloping 

 as seen in the longitudinal section (Plate II. Figs. 2, 4) very gradually 

 from a deptli of three fathoms to five and a half fathoms, when the slope 

 increases more rapidly to seven, ten, and then suddenly drops down to 

 over a hundred (140) fathoms. Transvei'se sections of the atoll show 

 well its gradual deepening as we proceed from the inner eastern edge to 

 the section across it near the western entrance of the lagoon. The floor 

 of the lagoon is of a very uniform depth transversely, as all the sections 

 taken from north to south readily show ; but the depth increases as they 

 are taken more to the westward (Plate II. Figs. 5-7), with the exception 

 of one or two small shallower patches, on which some Gorgonians and 

 algae are growing. On the western face, the coral heads are more devel- 

 oped near the two little islets firming the gate posts as it were to the 

 lagoon. They form a large broad patch, gradually passing on the one 

 hand into the broad ring of scattered coral heads below tlie 10 fathom 

 line on the western face of the atoll, and on the other hand into the 

 two narrow belts of scattered coral heads and patches of Gorgonians 

 found running along the interior of the lagoon more or less parallel 



