232 BARBOUR: ZOOGEOGRAPHY. 



tation from Watts makes clear. Thus, their real core has been, in some cases, 

 almost completely masked. The middle group is the dominant one, and has 

 become thrust up in many cases to form mountain chains of considerable height, 

 and to make all of the largest islands; while the outer series has given rise to 

 only low-lying areas, some of them, however, of great size. Florida and some 

 of the Bahamas, for instance, have a very considerable area. 



Suess does not, however, give many facts as to the actual formation of each 

 island, and the little information available is scattered far and wide in many 

 journals. For Grenada there is no paper dealing with the geology which is in 

 any way comparable to Guppy's Notes on a visit to Dominica, describing the 

 geological features of the island (Proc. Sci. assoc. Trinidad, December, 1869, 

 p. 377-392, 2 pi.). In view of this, the following quotation from an address 

 published in the London times by Dr. Francis Watts, Imperial Commissioner 

 of Agriculture for the West Indies, is of interest and importance : — 



"A glance at the map of the West Indies almost certainly gives rise to the impression 

 that the island represent the tops of a submerged land area, at one time connecting North and 

 South America. Geologists support this popular impression, and refer to this lost country 

 as Antillia, believing that it had an actual existence; but they are by no means agreed as to 

 the period at which it was in being. 



" Most of the islands bridging the gap across the Caribbean Sea show marked volcanic 

 characters. Thus if we consider the range from St. Thomas southward to Trinidad, we find 

 the Virgin Island group, Saba, St. Eustatius, St. Kitts, Nevis, Montserrat, Guadeloupe 

 (western half), Dominica, Martinique, St. Lucia, St. Vincent, the Grenadines and Grenada 

 all considered as volcanic, while St. Croix, Anguilla, Barbuda, Antigua, Guadeloupe (eastern 

 half), and Barbados are recognized as being built up extensively or entirely of sedimentary 

 and coral rocks. The study of these latter has afforded grounds for assigning geological dates, 

 more or less vague and tentative, to the various formations there found. 



"It is generally assumed, though not perhaps very definitely stated, that the volcanic 

 islands contribute little which will enable one to learn much of the past history of the chain 

 of which they constitute so large a part — a view, which, coupled with a misunderstanding 

 concerning the true nature of some of the rocks classed as volcanic, has impedded the advance 

 of knowledge in no inconsiderable degree. 



" Observations carried on for some time in the Island of Antigua have led to the conclu- 

 sion that the so-called volcanic rocks of that island — rocks to which previous writers have 

 referred as the oldest series, or the old igneous basement on which the latter series have been 

 superimposed — have not the character accorded to them, but that they are highly altered 

 and displaced portions of the sedimentary rocks which occur in an unaltered condition in the 

 middle of the island. 



" These unaltered sedimentary rocks, which have usually hitherto been wrongly described 

 as tuffs, contain fossils in places, though these are not abundant. They consist of sandstones 

 (often so fine-grained as to be mud stones) and conglomerates. Associated with these rocks 

 are considerable masses of fossil wood completely silicified and in most instances so well pre- 

 served that the minutest structure is capable of examination in microscopic sections. In 

 addition to these woods, there are associated with these rocks silicious masses containing 



