322 Physical Geography, etc. 



last two on the same Bank) is, in common with most of 

 the ishinds to the south, to and inclusive of Trinidad, distinct 

 from the fauna of the islands between and inclusive of the 

 Bahamas and Cuba, and the Anguilla Bank, on which are 

 Anguilla, St. Martin and St. Bartholomew.* 



This difterence of the faunas, and the well defined line of 

 their separation, must be considered in connection with the 

 past and present geological history of the Islands. 



The distribution of the species of the genera Macrocera- 

 mus and Atrophia illustrates in a marked manner the dis- 

 tinctness of the two faunas just mentioned. Macroceramus 

 has two species in the Bahamas (1 common to the Great 

 Bank, Florida and Cuba, M. Gossei, being the only species 

 found in Jamaica) ; 36 in Cuba, and 10 in Haiti of which 

 1 (M. Gundlaclii) occurs in both. 



There are two other species only in the islands between 

 and inclusive of Porto Rico and those on the Anguilla Bank, 

 M. signatus \fh\iA\ besides Haiti, is found in Tortola, Necker 

 Island and Anegada, all on the Virgin Bank, and in Anguilla 

 and St. Bartholomew on the Anguilla Bank; M. microdon 

 occurs in Porto Kico, Vieque, St. Thomas, Tortola and Ane- 

 gada. The genus is not represented in St. Croix, and not 

 in any of the islands south of the Anguilla Bank. 



Strophia has 16-18 species in the Bahamas of which 1 is 

 also in the Florida Keys, and at least 6 in Cuba ; 17 in Cuba ; 

 none in Jamaica ; 2 in Haiti, of which one, S. striaiella, 

 occurs in Cuba, Porto Rico, Necker Island and Anegada, 

 and the other, S. microstoma, is found also in Cuba, Haiti 

 and Porto Rico {fide Pfr.). Remains of a fossil species, im- 

 determinable, are noticed in Sombrero, and a fossil species 

 in St. Croix. There is no representative of the genus on 

 the Anguilla Bank or to the south of it. 



The exceptions are curious, Macroceramus Gossei and 

 Strophia uva are found in Curacao ! f 



* See Bland, Proc. Anier. Phil. Soc, Z. c. 



fl desire to acknowledge my obligations for specimens and the means generally 



