West India Land Shells. 335 



XXXIII. — On the Geographical Distribution of the Genera 

 and /Species of Land Shells of the ^Yest India Islands; 

 with a Catalogue of the Species of each Island. 



By Thomas Bland. 



Read, June 17, 1861. 



The researches carried on, especially during the last fifteen 

 years, have developed the extraordinary ricline?^s in Land Shells 

 of the West India Islands. To the late Professor C. B. Adams 

 belongs to a great extent the merit of directing the attention of 

 ^Naturalists to the subject, and it has, since tiie result of his first 

 visit to Jamaica was pubUslied, been zealously followed up. 



The "West Indies consist of a curvilinear chain of islands 

 extending in a soutli-east and then southerly direction from the 

 coast of Florida in North America, to the Gulf of Paria, on the 

 east coast of Yenezuela in Soutli America. The portion of the 

 Atlantic Ocean, in a manner inclosed by these islands and the 

 shores of the adjacent continents, is divided into two great 

 basins — the Gulf of Mexico and the Caribbean Sea. The for- 

 mer is separated to a onsiderable extent from the latter by the 

 Island of Cuba, the western end of which lies about midway 

 between Florida and the peninsula of Yucatan ; the distance 

 from the island to Florida being about 140, and to Yucatan 

 about 120 miles. The Gulf of Mexic* is about 1000 miles long, 

 and has an average width of 650, or thereabouts. The Carib- 

 bean Sea is in length liOO, and in width at the narrowest 

 part about 400 miles. 



The islands are divided into t'iree groups, viz. the Bahamas, 

 the Great Antilles (Cuba, Jamaica, Hayti, and Porto Rico), and 

 the Lesser Antilles ; the area of the first group is estimated to 

 be 5,42±, of the second 75,6;;8, and of the last, 4,961 square 

 miles. Of the great Antilles, Cuba, with the Isle of Pines, 



JUNE, 1861. 23 Ann. Lto. Nat. Hist. Vol. VII. 



