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bulletin: museum of comparative zoology. 



mushroom-shaped. A passage has been cut for boats through the shal- 

 low opening connecting the lagoon with tlie inner sound, which receives 

 the drainage of the interior of the depressed basin. The elevated lime- 

 stone bluff's extend from the northern horn of the rim, along the coast 

 line, towards the landing place on the north face of the island. To the 



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3IANGO, SEEN FROM THE NORTHEAST. 



east of this, on the north shore, are fine bluff's of elevated limestone, 

 weathered into dome-like lamellar masses, with rounded masses and 

 mushroom-shaped heads at the base (Plate 86). A little farther west, 

 on the beach beyond the bluff's, the underlying volcanic I'ocks crop out 

 again, and from there south the negro-heads on the western reef flats 

 are all of volcanic origin. 



The island of Mango is almost circular, about three miles in diameter, 

 surrounded by a barrier reef, which passes into a fringing reef off" the 



northern coast near the landing, 

 and off a part of the southeastern 

 face of the island. The inner 

 lacfoon is verv narrow, not more 

 than a quarter of a mile in width, 

 and also very shallow. Its great- 

 est depth is about two fathoms, 

 and it is further studded with 

 negro-heads and coral patches, 

 thus protecting the lagoon to a 

 certain extent from the invasion 

 of the sea. The ridge of elevated 

 coralliferous limestones on the 

 west side of the island extends 



MANGO LANDING, VOLCANIC sciBSTRATUM. '^^ far as the first islct on the 



south face of Mango. There the 

 central volcanic ridge which has raised the reef joins the western edge 

 of the rim of the island. The ridge runs in a southerlv direction, at a 





