OVERLAND TO LA ESPERANZA 35 



reasonably certain that the three subfaunal pro- 

 vinces once constituted three separate islands. 

 Such was the condition at the close of the Jurassic 

 period and continued through the Tertiary epoch. 

 At the close of the Tertiary, the mere yesterday of 

 geologic time, the Havana province was raised 

 from a shallow sea and its hilltops appeared as an 

 archipelago of small islands. These derived their 

 fauna from both the large islands then existing — 

 the Organ Mountains to the west and the Trinidad 

 Mountains to the east. The last chapter in Cuban 

 geological history has been the successive eleva- 

 tions of coral reefs built upon her narrow island 

 shelf. Here we find a suitable home for land-shells 

 in a limestone rock and soil but with life and food 

 conditions different from that of the high sierras. 

 The species that have migrated there from other 

 and older regions and have survived the changes 

 of environment have become modified into a group 

 of almost subfaunal importance. 



The remarkable land-shells of Cuba have been 

 made known to science chiefly through the efforts 

 of four distinguished naturalists, who combined 

 with their interest in mollusks an equally great 

 interest in other forms of Cuban life. The first 



