6 WALTER K. FISHER, 



between the epithelial cells, their bases resting on the basal membrane. 

 But they are also bound one with another by the thin cuticle which 

 covers the lips. In Acmaea digitalis Thiele ^) has described similar 

 structures but his figure (105) shows that they are simply projections 

 or tiny spines on the cuticle, very similar to those on the palps of 

 Lottia gigantea presently to be described. It is probable that these 

 teeth in some way aid in scraping, or at least retaining small particles 

 of food {At Figs. 7, 18). 



The mouth leads directly into a spacious buccal or oral cavity. 

 Within this the following features are to be noticed: the jaw, palps, 

 radula, sublingual organ, subradular pouch, sublingual groove, and 

 lateral pouches. The jaw is a rather pliable structure, and bounds 



Fig. D. Cross section through head in region of mouth, to show sublingual organ 

 and palps. At area of teeth on lips, BC buccal cartilages, B. S buccal sinus, C. P. C 

 cerebro-pedal connective, C. PI. C cerebro-pleural connective, Df dorsal fold of pharynx, 

 J jaw, 31 muscles of tentacle, N nerves in tentacle, Ph pharynx, Pp palps, Sg sensory 

 groove of lips, Stib. L sublingual organ, T tentacle. 



the forward side of the oral cavity. It bends backward and downward 

 at either side and forms a deep horny trough in the "upper" or 

 forward lip. As has been suggested by Thiele this structure probably 

 protects the lip from the radula teeth. But the heavy muscles at- 

 tached to it would suggest that it also serves a more active function. 

 It is noteworthy in this connection that the subradular furrow (Fig. 11, 

 Sub.L.F) serves the same purpose for the lower or hinder lip, and 



1) Die systematische Stellung der Solenogastren und die Phylogenie 

 der Mollusken, in: Z. wiss. Zool., V. 72, 1902, p. 338. 



