RELATIONSHIP OF THE FAUNA. 87 



cated which extends probably far beyond the time that is 

 generally associated with the making of "recent" coral 

 islands. 



The number of terrestrial moUusks credited to the Bermudas 

 is usually given at 19 or 20, but the list which appears further 

 on shows that this number must be increased to 30. An anal- 

 ysis of this list indicates that of the thirty species sixteen, or 

 somewhat over half, are known also from the West Indian 

 islands, five {Helix vortex, H. microdonta, H. pulchellaf, H. 

 appressa, and Pupoides fallax) occur in the United States, three 

 in Europe or the East Atlantic islands (Madeira, Azores — Helix 

 ventricosa, Helix pnlchella, Csecilianella acicida), while not less 

 than eight, including all the species of the remarkable group 

 Pwcilozonites, appear to be confined to the Bermudas. These 

 species are : Helix discrepans, Pwcilozonites Bermudensis, P. cir- 

 cumfirmata, P. Reiniana, Succinea Bermudensis, Alexia Bermuden- 

 sis, Melampus Redfieldi, and Helicina convexa. To this number 

 may perhaps also be added the somewhat doubtful Helix 

 hypolepta. The large proportion of special forms, taken in con- 

 junction with the development of a distinct group, is certainly 

 remarkable in the case of an island group which has been 

 generally considered to be recent in formation, but this spe- 

 cialization is also well marked in some of the other animal 

 groups. The fact argues for considerable antiquity, and it is 

 interesting to note in this connection that the ancestral type of 

 the peculiar molluscan genus Poecilozonites is represented in 

 the common sub-fossil P. (Helix) Nelsoni, the probable progeni- 

 tor of the recent P. (Helix) Bermudensis. 



The conditions governing the dispersal of the terrestrial 

 Mollusca have been fully discussed by Mr. Darwin and Mr. 

 Wallace, and there can be little or no doubt that their explana- 

 tion of the oceanic transport of these animals is the true one. 

 The floating material of the Gulf-drift has in this instance, 

 doubtless, sufficed to bring most, if not all, of the non-peculiar 

 species of the islands from the West Indies and the Southern 

 United States. A few of the species, again, may have been 



