Part 3.— THE CYCLOPHORID MOLLUSKS OF THE 

 MAINLAND OF AMERICA 



By Paul Bartsch and Joseph P. E. Morrison 



Family CYCLOPHORIDAE Gray 



The family Cyclophoridae is defined on p. 3. 



The mainland cyclophorids range from Mexico to and over South 

 America. They belong to four subfamilies, which the following key 

 will help to differentiate : 



KEY TO THE SUBFAMILIES OF CYCLOPHORIDAE ON THE MAINLAND OF AMERICA 



Shell elongate-turrited Megalomastominae 



Shell not elongate-turrited. 



Shell pupoid Diplommatininae 



Shell not pupoid but planorboid or helicoid. 



Operculum chondroid Amphicyclotinae 



Operculum calcified Aperostominae 



Subfamily Megalomastominae Torre and Bartsch 

 For definition of the subfamily, refer to p. 3. 



Genus TOMOCYCLUS Crosse and Fischer 



1872. Tomocyclus Ceosse and Fischer, Journ. Conchyl., vol. 20, p. 76. 



Shells with elongated-turrited spire. Aperture circular, peristome 

 double ; the inner more or less exserted ; the outer broadly flaringly ex- 

 panded, with a slit terminating in a more or less circular perforation in 

 the parietal wall below the edge of the peristome. Operculum with 

 central nucleus, bearing a broadly expanded spiral lamella, which is 

 reflected to parallel the basal chondroid plate. The outer edge of the 

 lamella may be appressed to the succeeding turn, or fringes of its outer 

 ragged edge may be free ; in reality the entire lamella is free, and its 

 appressed position is responsible for its appearing adnate. 



Type : Tomocyclus gealei Crosse and Fischer. 



T. siinulacrum (Morelet) yields the following data : Radula formula : 

 3:3:3:3. Jaws with central projection. Penis on right side of neck 

 traversed by a groove only. 

 142 



