32 University of Michigan 



to irrigate the strip of plantation. The shells are very- 

 numerous on the rocks, in both the reservoir and the brook. 

 The water is truly potable. 



Station Bel. Pos Baca (pi. II, C; L68° 16.32', 12° 8.44'). 

 South of Kralendijk, the low plains of recent limestone con- 

 tain numerous sink-holes, which may form small caves; if 

 these reach the level of the ground water, they become natural 

 wells. The different cavities have a wide range in the saline 

 content of the water; in some it is quite fresh, in others dis- 

 tinctly brackish, while the salt pans contain highly concen- 

 trated sea water. That of Pos Baca (fig. vi-15) is slightly 

 brackish, but is used for stock animals, while that of Pos 

 Frances, which contains small fishes, is potable. 



Station Kcl. Pos di Cas (Z; L68° 17.56', 12° 9.70'). Klein- 

 Bonaire is very similar in structure to the southern portion of 

 Bonaire, and contains several sink-holes which make natural 

 wells. One of these forms a small cave near the only habita- 

 tion on the island; the water is slightly brackish, but drink- 

 able. Analagous cavities are also present on Klein-CuraQao ; 

 the water in one of these is drunk by goats, but no freshwater 

 shells were found. 



Native Species 



neritidae 



Neritina zebra (Bruguiere) 



N. zebra Martens (1879; Chemn., II, 118) ; collected by Deplanche. 



Type locality: Cayenne, Guiana. 



Distribution: Brazil to eastern Venezuela; Panama? Cur- 

 asao. I did not obtain this species. Possibly it has been ex- 

 terminated by the conversion of many "salinjas" into salt 

 pans. 



Theodoxus meleagris (Lamarck) 



Type locality: Rivers of Santo Domingo. 



Distribution: South Carolina, Bermudas and Mexico, to 

 Brazil. Curasao : five dead and one living juvenile specimen 

 from the inner end of Sint Kruis Baai (Cdl6). 



