2 University of Michigan 



organ-pipe cacti. The south-east end, near Willemstad, is 

 lower, less broken, and noticeably more arid. From its color, 

 much of the rock outcrop at the northern end appears to be 

 metamorphic or igneous, but the south shore is entirely of a 

 coral-reef formation. 



On March 28, and again on May 6, 1920, a few hours col- 

 lecting at the east edge of Willemstad netted a considerable 

 number of shells. The abundance of Cerion was astounding; 

 practically every bit of vegetation was almost covered at the 

 base with sstivating individuals. I estimated that there were 

 about 50 specimens per square meter examined. 



The place collected is Schaarlo, just behind the lagoon 

 east of the harljor. This hill is entirely composed of porous 

 limestone, somewhat like that around Nassau in the Bahamas. 

 The vegetation is very scanty and consists mainly of Opuntia- 

 like cacti and prickly pears, with some of the larger organ-pipe 

 cacti, mimosa and evergreen thorn-bushes reaching a height 

 of about 6 meters. Extreme dessication is the predomniant 

 feature of the landscape, and 1 am told that it rains very 

 rarely. All of the living shells collected were Kstivating 

 either on the lower stems of bushes and cacti (mainly Cerion), 

 or in crevices between and under the rocks and rock-frag- 

 ments. 



ANNULARIID.E 



Tiidora mcgachcilos (Potiez and Michaud). 



Quite abundant; mainly under bits of coral rock and in 

 crevices, but rarely found aestivating on the vegetation. This 

 species is very variable, in color, size and sculpture. The 

 males are considerably smaller than the females, and tend to 

 be more brilliantly colored. The coloration may be classified 

 as follows : 



