PLATE XIII. 



Page. 



IDONEARCA VULGAIilS MoitOD 98 



Fig. 1. Lateral view of a cast of the usual form ol the species. 



2. Autcrior profile view of the same. 



3. Lateral view of a cast of an old and thickened spccimuu. 



4. Cardinal viow of the same. 



5. View of a cast of a single valve, showing the outline of the shell iuul teolh. 

 Idoneahca ANTnosA Morton 0(j 



Fig. 6. Lateral view of a cast of medium size. 



7. Anterior profile view of the same. 



8. Lateral view of another, larger but imperfect cast. 



9. Auterior profile view of the same. 



10. View of the exterior of a specimen from the limestone nodules from Holmdol, N. J. 



This is the form described by Mr. Gabb as /. veglecta. 

 IL View of a ca.st which retains the shell on one valve partially showing the teeth, 



which are represented on the posterior side as obtained from a gutta-percha 



cast in the shell of the opjiosite valve. 



294 



