of West India Zand Shells. 347 



and Chondropoma, the occurrence of the only species of Titrina, 

 and the absence of Proserpina and genera peculiar to Jamaica. 

 Stropliia and Megalomastoma, which prevail in Cuba, but are 

 not in Jamaica, are represented in Haiti. The only insular 

 species of Simpulo])si8 are in Haiti and Portorico ; those two 

 islands, nearly equidistant from North and South America, 

 have not the species of Orthaliciis which inhabits both sections 

 of the continent and the ishmds more immediately adjacent to 

 them. I should remark that several of the species common to 

 Cuba, Jamaica, and Haiti, are otherwise widely distributed. 



No other conclusion, under all the circumstances stated, can 

 be arrived at, but that Cuba with the Isle of Pines and the 

 Bahamas, Jamaica, and Haiti, are entitled to be ranked as 

 three distinct zoological provinces; although Haiti has cer- 

 tainly more relationship with Cuba on the one side and Por- 

 torico on the other, than exists between it or Cuba with 

 Jamaica. 



Portorico (with Vieque) is characterized by the occurrence 

 of the only species of Clausilia, and one of Tornatellina, two 

 South American genera, absent on the islands w^estward, a single 

 one of Stoastoma, the absence of several genera of Cyclo- 

 stomace^e which are found in the islands to the westward, by 

 the increased number of Bulimi relatively to Helix, and the 

 diminished representation of Macroceramus and Pupa. Por- 

 torico is unmistakably related to St. Croix, St. Thomas, St. 

 John, Tortola, Anegada, St. Bartholomew, and Anguilla, as 

 those islands are inter se. Megalomastoma* is not represented 

 further to the eastward of Portorico than St. John (I am not 

 certain as to Tortola), and Macroceramus than Anguilla, to the 

 south of which neither of them occurs. Enneaf has one species 



* Megalomastoma is found fossil in the Eocene strata of the Isle of Wight and 

 Paris. 



•j" As to thp occurrence of Ennea bicolor Gould in St. Thomas, eee my remarks 

 in the Annals VI. p. 147. Mr, Theo. Gill subsequently discoTtred the same spe- 

 cies in Trinidad ; its occurrence there also is & curious fact. 



