TONGUES OF MOLLUSCA. 81 



SO, the long ribbon, coiled up like a watch-spring, cannot 

 fail to be found. 



In the Trochuses, and indeed in all the Scutibranchiata, 

 one point of the scissors should be introduced into the 

 mouth of the animal, and an incision made directly back- 

 wards in the middle line above to some distance behind 

 the tentacles ; the tongue is then immediately brought into 

 view, lying along the floor of the mouth. 



EXPLANATION OF PLATES. 

 Plate IV. 



Cyclobranchiata, 

 Fig. I. Patella vulgata. Fig. 4. Acmsea patina (profile). 



Fig. 2. Patella pellucida. Fig. 5. Tecturella grandis. 



Fig. 3. Acmaea pelta. 



Plate V. 



Scutibranchiata. 

 Fig. I. Trochus zizyphinus. Fig. 3. Fissurella nigropunctata. 



Fig. 2. Haliotis (sp. from California). 



Plate VI. 



Pectinibranchiata. 

 Fig. I. Buccinum undatum. Fig. 4. Natica monilifera. 



Fig. 2. Purpura biserialis. Fig. 5. Luponia vitellus. 



Fig. 3. Cerastoma Nuttalli. 



Plate VII. 



Anatomical details of Lingual Apparatus. 



Fig. I. Patella (American species), with the tongue protruded. (Magnified.) 



Fig. 2. Patella vulgata. The head opened above, showing the lingual ap- 

 paratus. (Magnified.) 



Fig. 3. Patella vulgata. The foot removed, showing the reserve ribbon. 



Fig. 4. Acmsea (American species), showing a long loop of ribbon on the back. 



Fig. 5. Purpura melones, showing the trunk. 



Fig. 6. Murex erinaceus, showing the trunk and free coil of ribbon. (Mag- 

 nified.) 



Fig. 7. Buccinum undatum : the trunk partly protruded. 



SER. III. VOL. II. G 



