Hello Peter,
The publications department of the Museum of Comparative Zoology at Harvard
University offers a number of papers either on Cerion specifically, or more
generally on land snails of various Caribbean locations. Among these is "A
Catalog of the Cerionidae" by William Clench. You can review the museum's
available molluscan publications at:
http://www.mcz.harvard.edu/Departments/Mollusks
Regards,
Paul Monfils