194 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
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. 
Jartholomew, 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 tho 
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 débris ; 
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. i 
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, Nevis, 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 Guadeloupo, 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 voleanic extrusion was the main chain, or belt 
of islands on the Caribbean side, and that the other islands of organic 
