494 H. A, Pilshry — Air-breathing Mollusks of the Bermudas. 



It is obvious that in dealing with certain Antillean species, such 

 as Opeas^ it is not possible to rigidly discriminate between those 

 introduced by natural means and those imported by man. The 

 earlier faunal lists are our chief dependence in such cases. The 

 same difficulty is encountered in deciding upon the primitive flora 

 of the islands, and of course attends all work on insular faunas or 

 floras at the present day/ 



Oceanic characteristics. — The foregoing data expose the truly 

 *' oceanic " nature of the fauna, which is a peculiarly disharnionic 

 assemblage, to use Baur's expressive term. The endemic element 

 (Poecilozonites) undoubtedly long antedated the other forms, as its 

 generic divergence and strong specific differentiation indicate. In all 

 probability it was derived from the eastern United States by some 

 rarely efficient means of transport. The remaining forms are all 

 Antillean in their affinities, and probably a drift or flotsam fauna. 

 But the Antillean element by itself is not harmonic, for the absence 

 of Cerion, Urocoptidm, belogonous or epiphallogonous Helices, and 

 oyclostome operculates, all eminently characteristic of the West 

 Indian faunas, betrays the hand of what we call chance, or the 

 rigorous selective action of an over-sea journey, in the Bermudian 

 assemblage. 



List of Species. 



Family HELICID-ffi. 

 Helicella (Cochlicella) ventricosa (Drap.). 



First reported by Temple Prime in 1852. It has been noticed by 

 all later collectors, and it is now exceedingly abundant. 



It is common under the scales of cycad trunks, and in crevices of 

 bark and knot holes of other trees. Also under the bark of fallen 

 trees. — (Cook.) 



' As early as 1615-20, or immediately after the first settlement, expeditions were 

 sent to the Bahamas to introduce various useful tropical plants in growing condition, 

 as well as seeds. Among the plants enumerated as introduced at that time and with 

 which snails and insects may have been introduced, were the pineapple, papaw, sugar- 

 cane, banana, plantain, cassava, orange, lemon, and many others. 



At about the same time various useful plants were also introduced from Virginia 

 and from England. " Vines and cuttings of vines " were sent from England about 

 1616. 



