PLATE I 



SURFACE FEATURES OF CERITHIUM AND VUI.GOCERITHIUM 



Diagram to illustrate the development of five surface features on eleven 

 recent species of Cerithium and Viilgocerithium vidpatum. 



The numbers at the left of the plate indicate the numbers of the volutions, 

 the protoconch being numbered 1. 



= primary spirals. 



I 

 I 



> 



= ribs. 



^outline of volution. 



= spirals of secondary and higher orders. 

 = nodes. 



