598 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



GENERAL RELATIONS. 



The boundaries of the Gulf of Mexico and the Caribbean Sea form 

 a parallelogram (see pi. 73) ; those on the north and south extend 

 along east and west lines, those on the east and west are northwest 

 to southeast, while the basins are separated by cast and west 

 structures. 



The bottoms of the continental slopes on both sides of the continents 

 range between 2,500 and 3,000 fathoms in depth. On the east the 

 2,500-fathom curve is either at or near the base of the slope from off 

 the Banks of Newfoundland southwestward to off Jacksonville, 

 Florida, whence it bends toward the southeast, passing east of the 

 Bahamas, north of Porto Rico, east of the Caribbean arc, east of 

 Trinidad, and northeast of the Guianas. The 2,500-fathom contour 

 lies farther offshore on the Pacific side than on the Atlantic side of 

 North America, but is nearer shore from the Revilla Gigcdo Islands, 

 west of Manzanillo, Mexico, to off Guatemala, whence southward the 

 2,000-fathom contour is near the base of the slope until off Peru, 

 where there is a drop to over 3,000 fathoms in the great Callao deep. 



Land areas bound the Gulf of Mexico on the east, north, west, and 

 south. The land on the west continues without interruption through 

 Central America and northern South America, forming the western 

 and southern boundaries of the Caribbean Sea. Between southern 

 Florida and Trinidad there are relatively shallow-water connections 

 with the Atlantic Ocean through passages between Florida and Cuba, 

 and through passages between both the Greater and the Lesser Antil- 

 les to Trinidad. Depths of about 1,000 fathoms or somewhat more 

 are found between Cuba and Haiti in the Windward Passage, and 

 between Anegada and Angtiilla in the Anegada Passage, but they are 

 usually less than 500 fathoms. 



The Gulf of Mexico is separated from the Caribbean Sea by the 

 Yucatan Peninsula and Cuba, but connects with it through the Yuca- 

 tan Channel. The deepest part of this basin, which is a simple basin, 

 is slightly over 2,000 fathoms. 



The Caribbean Sea is a compound basin, separated into two parts 

 by the ridge that extends from Honduras to Jamaica. The northern 

 division is almost subdivided by the Cayman ridge, which extends 

 westward from the Sierra Maestra of Cuba. Depths of 2,500 fathoms 

 are attained between the Caymans and Cape San Antonio, Cuba, 

 while south of them depths exceeding 3,000 fathoms are recorded in 

 the Bartlctt deep. The southern division is a simple basin with 

 depths ranging between 2,250 and 2,900 fathoms. 



The data presented show that these two basins are land-locked, 

 except that between Florida and Trinidad shallow passages between 

 land areas connect with the Atlantic Ocean, that the two basins are 

 separated by structures transverse to the continental trend in Yucatan 



