374 



R. T. GUNTHEE. 



of cliitinous elements near the mouth. And if this were to 

 happen in the mid-ventral line a radula would result. At 



Text-fig. 7. — Buccal armature of Clio borealis. 

 h. "Hooks." r. Radula. 



Text-fig. 8. — Buccal armature of Cliffitognatha and Ampliineura. 

 a. Krolniia hamata (after Fowler), b. Sagitta serrato-dentata. 

 c. Sagitta bipunctata (after Fowler), d. Lei)idomeina (after 

 Kowalewsky). e. Proneomenia (after Ilubrecht). 



the same time it must be remembered that the radula is 

 absent in several Amphineura and in Lamellibranchia; in the 



