Occasional Papers of the Museum of Zoology 109 



Two dead specimens were obtained from leaf mould along 

 the road at Campo Klein Piscadera (CbT). This species has 

 been widely distributed by commerce. 



ZOOGEOGRAPHICAL AFFINITIES OF THE ]\IOLLUSCAN FaUNA 



In the study of the terrestrial, molluscan fauna of these 

 islands, five, salient characteristics appear. (1) There is a very 

 high percentage of endemism. (2) Sublittoral, limestone-loving 

 species preponderate. (3) Typically South American groups 

 are completely absent. (4) Several Antillean groups form 

 conspicuous components of the total population. (5) Neverthe- 

 less, the closest affinities showTi by any of the individual species 

 are with forms from northern South America. 



Two genera (Stoastomops and Cistulops), three subgenera 

 (Bonairea, Neosubulina s. s., and Cerion s. s.), and a section 

 (Tudora s. s.) are, as far as known, endemic to the Dutch 

 Leeward Islands. Only three of the well-established species, 

 Drymaeus virgulatus, Thysanophora crinita and Oxystyla 

 maracaihensis, are known to extend their range beyond the 

 islands. The first of these is a species of Porto Rico and the 

 northern Lesser Antilles. Although it is certainly widespread 

 in the undisturbed portion of the Dutch Leeward Islands, its 

 remarkably discontinuous distribution, as already indicated, 

 arouses the suspicion that its dissemination may be due to the 

 agency of man. The last two are species of northern South 

 America, and only reach Aruba (although T. crinita was 

 found in ruderal conditions on Curacao) ; the Oxystyla ap- 

 pears to be entirely subfossil. 



The endemism of the fauna of Bonaire, Klein-Bonaire and 

 Curasao is readily accounted for on the basis of their geo- 

 graphic isolation. As already described, the depth of ocean 

 between these islands and the mainland indicates a separation 

 at least as remote as that between South America and the 

 northern Lesser Antilles. Aruba, on the other hand, lies in 

 quite shallow water, and it is rather remarkable that its fauna 

 does not contain an even larger proportion of South American 

 invaders. 



