FISSURELLID.E. 141 



types. Nearly all of the tertiary species, both of Europe and Amer- 

 ica, described as " Fissurella" belong to the genus Glyphis- a genus 

 which is shown herein to have no especial relationship to Fissur- 

 ella proper, beyond the bond of belonging to the same family. 



Synopsis of Subfamilies of Fissurellidce. 



Subfamily I. FISSURELLIN^E Pilsbry. 



Apex of shell wholly removed by the anal perforation, which is 

 bounded inside by a callus with entire margins, not truncated or 

 excavated posteriorly. Central tooth of the radula narrow. Shell 

 wholly external, capable of containing the entire animal. 



Subfamily II. FISSURELLIDIN^E Pilsbry. 



Apex of shell wholly removed by the large anal perforation 

 which is bounded inside by a callus with entire margin not trun- 

 cated posteriorly. Central tooth of radula much broader than the 

 adjacent laterals. Mantle generally enveloping shell and foot, 

 wholly or in part ; the animal much too bulky to be contained in the 

 shell. 



Subfamily III. EMARGINULIN^ Pilsbry. 



Apex of shell generally not removed, the anal tube occupying an 

 anterior slit, notch or sinuation ; or if apex be removed by a per- 

 foration, the hole is provided internally with a shelf or septum project- 

 ing forward and downward from behind it, or if bounded by a callus, 

 the latter is truncated or excavated posteriorly. Central tooth of 

 radula broad. 



Synopses of and keys to the genera are given under each of the 

 subfamily heads, where also the characters of each subfamily are 

 discussed in detail. 



Subfamily I. FISSURELLIN^E Pilsbry. 



Animal not too large to be contained in the shell when in a state 

 of rest. Rhachidian tooth of the bilaterally symmetrical radula nar- 

 row, like the lateral teeth on each side of it, and having a well- 

 developed cusp at its apex. Shell with the apex wholly removed 

 by the subcentral or anterior perforation, which is bounded inside 



