12 IN LOWER FLORIDA WILDS 



about one hundred species of native plants which 

 are found nowhere else in the United States. 

 Liguus solidus, a large, beautiful arboreal snail, 

 exclusively occupies these islands and has formed 

 several well marked subspecies, but it does not 

 occur on the mainland. One particular form 

 which may have originally sprung from it is found 

 on Lignumvitae and on Lower Matecumbe keys 

 of the upper chain, but it probably reached these 

 islands by drifting from the lower chain. Another 

 large tree snail (Oxystyla resus) has evidently de- 

 veloped on the Lower Keys and is only found else- 

 where on Key Vaca, an island of the upper chain 

 but lying close to the lower ones. Hemitrochus 

 varians, a finely colored Bahaman snail, is abundant 

 on the southeast coast and Upper Keys, but is not 

 found on the lower ones. A native cotton rat and 

 a cotton mouse, which I shall mention elsewhere, 

 occur abundantly on the upper chain of islands 

 but never on the lower. So far as we know, no 

 mammals are indigenous to any part of the lower 

 group. 



The mainland of the Miami region, including the 

 rocky ridge just mentioned, has a mixed flora, a 

 majority of its species being migrants from the 



