ENDODONTA. 25 



don, Ptychodon, Helenoconcha} have received names. These divis- 

 ions or " sections " are of doubtful value, as they are practically 

 undiagnosable ; but still they are natural groups of species, and as 

 such have their uses. 



Sections of Endodonta. 



a. St. Helena forms Helenoconcha. 



aa. Australo-Polynesian forms 



b. Shell acutely keeled ; teeth generally large, rarely wanting 



Endodonta s. s. 

 bb. Shell rounded at periphery 



c. parietal wall with one or many line, outer lip toothless 



Nesop lii/K. 



cc. outer lip toothed or lirate; parietal wall generally 

 toothed Ptychodon, Thaumatodon. 



Section Endodonta s. str. 



Shell openly or widely umbilicated, depressed, carinated, opaque; 

 aperture obstructed by internal lamellae, of which there are one or 

 two on the parietal wall and several on the basal wall (but in E. 

 fabrefacta lamella are absent). Type E. lamellosa Fer., pi. 4, figs. 

 40, 41. (see also E. obolus Old., pi. 4, fig. 39 ; and E. fabrefacta Pse., 

 pi. 5, figs. 52, 53). 



Radula having 12-6-1-6-12 teeth. Centrals square, tricuspid ; 

 laterals of the same size as the centrals, bicuspid, the entocone 

 being absent. Marginal teeth having a long bifid inner cusp and a 

 short bifid ectocone (PI. 9, fig. 22, E. huaheinemis Pfr.). 



Sandivich Island species. 



E. apiculata Anc. viii, 95. E. lamellosa Fer. iii, 67. 



E. binaria Pfr. iii, 61. E. laminata Pse. 



E. fricki Pfr. iii, 67. E. rugata Pse. iii, 67. 



Society Island species. 



E. cretacea Grt. iii, 66. E. obolus Gld. iii, 61. 



E. fabrefacta Pse. iii, 45. acetabidum Pse. 



conicava Mouss., Schm. celsa Pse. 



v. picea Grt. barfti Grt. 



E. ficta Pse. iii, 62. intennixta Mouss. 

 E. garrettii Auc. viii, 95. 



