58 University of Michigan 



Measurevients (continued) 



Shell Aperture Operculum Whorls 



alt. min. diam, alt. diam. long wide 

 from figures 

 (1838) 16.3 57( 9.3) 53(8.6) 90(7.7) 5 



simile Sowerby 

 from figures 

 (1843) 14.7 68(10.0) 48(7.0) 91(6.4) 4% 



19.0 66(12.5) 50(9.5) 85(8.1) 4% 



cancellatum Pfr. 

 from figures 

 (1847) 20.3 69(14.0) 52(10.6) 80(8.5) 36(7.4) 68(5.0) 41/2 



form desculpta, new 



male (C5cd) 13.1 69( 9.0) 55(7.2) 90(6.5) 37(4.9) 78(3.8) 3% 

 female 

 (type, C5cd) 16.8 69(11.5) 52(8.8) 89(7.8) 37(6.2) 82(5.1) 414 



C5cd. Quite abundant (359 specimens collected). The Schaarlo (C5c) 

 back of Willemstad is probably the type locality of this species, and this 

 lot is that described above (see Table VI). It contains a large propor- 

 tion of shells with vestigial spiral sculpture (form desculpta). 



C5ab. Quite abundant (186 specimens). Very similar to typical lot, 

 but with considerably less tendency to approach form desculpta. 



C4. Quite abundant (169 specimens). Sculpture heavy, and with a 

 tendency for the growth threads to coalesce. A few specimens are some- 

 what cancellate, and thus show a slight tendency to approach Icabrietensis. 

 Form desculpta appears to be absent. 



Tudora megacheilos spreitensis, new subspecies 



Type locality: (C8) at base of northern escarpment of 

 Seroe Spreit, Curasao. 



Distribution : Curagao ; western side, from Kaap Sint Marie 

 to Seroe Qtiinta, west to Sint Anna Baai, where it inter- 

 grades with typical megacheilos and form desculpta; invades 

 the region of the older rocks at Campo Bleinheim, and prob- 

 ably intergrades with rondeklipensis east of Bullen Baai (C6, 

 7, 8, 9, 13, Cb6b). 543 specimens collected. 



Shell (fig. xiii-C) : considerably heavier and larger than 

 typical megacheilos. Color : similar in pattern to megacheilos, 

 but usually more vividly colored and more distinctly banded. 

 Sculpture of last whorl (fig. x-35) : growth-cords heavieT", 

 more prominent, and more widely spaced than in megacheilos ; 



