194 BULLETIN: MUSEUM OF COMPAP.ATIVE ZOOLOGY. 



appear as the members of a kindred archipelago. The Virgin Islands at 

 the north are Antillean, while all south of Grenada are South Amer- 

 ican in natural relations. Barbados may also be distinctly related 

 to the latter category. Even after detaching these termini the remain- 

 ing islands of the archipelago lying between the Anegada Passage and 

 Tobago, constituting the Caribbee group, present almost as complicated 

 compositions. Some of the northern islands, such as Santa Cruz and St. 

 Bartholomew, are also Antillean in structure, and were it not for the deep 

 Anegada Passage, which almost severs the latter from the submerged 

 platform of the Antilles and their presence on a similar platform at the 

 north end of the Windward Channel, they might probably be considered 

 as Antillean. 



The Caribbee chain, however, south of the Anegada Channel and 

 north of Trinidad, constitutes a distinct geographic and geologic type, 

 which may be classified by composition into three general sub-types as 

 follows: (1) Volcanic islands composed entirely of igneous material; 

 (2) Islands composed entirely of organic oceanic sedimentary debris ; 

 and (3) Compound islands, with a higher summit region of volcanic 

 rocks of the first mentioned class, with added areas or benches of sedi- 

 mentary rocks. These three types are exemplified in Martinique, 

 Barbuda, and Antigua. 



The Caribbee chain is divisible into two parallel belts extending 

 the length of the archipelago. The innermost of these, facing the 

 Caribbean, including Saba, St. Eustatius, St. Christopher, Xevis, Mont- 

 serrat, Basse Terre, Guadeloupe, Dominica, Martinique, St. Lucia, St. 

 Vincent, the Grenadines, and Grenada, are composed almost entirely 

 of purely volcanic summits. These islands constitute the newest and 

 highest summits of the Windward chain, attaining heights approxi- 

 mating 4,000 feet in all the islands mentioned except the two most 

 northern, Saba and St. Eustatius, which rise to 2,820 and 1,950 feet 

 respectively, and the Grenadines. 



The eastern belt, composed of the sedimentary and compound type, 

 includes Sombrero, Dog, Anguilla, St. Martin, St. Bartholomew, Bar- 

 buda, Antigua, the Grande Terre of Guadeloupe, Marie Galante, and 

 Desirade. 



Barbados perhaps belongs in a class entirely by itself, lying to the 

 eastward of the chains mentioned. 



The arrangement of the islands as borne out by the stratigraphy 

 shows that the axis of volcanic extrusion was the main chain, or belt 

 of islands on the Caribbean side, and that the other islands of organic 



