LIST OF PLATES. XI 



Plate XVI. 

 1. Aporrliais pes-pelicani ; so named from the resemblance of 



tlie outer lip to tlie webbed foot of a bird. 

 3. Turritella communis. 



3. Cacum trachea. 



4. Buccinum undatum, or common Wbelk. 



Plate XVII. 



1. Mangelia septangularis. 4. Murex er'maceus. 



2. Mangelia Uirricida. 5. Natica monilifera. 



3. Tricliotropis borealis. 6. Purpura lapillus. 



1 . Natica Alderi ; showing the mentum and fold of the foot 

 partly enveloping the shell. 



Plate XVIII. 



1 a. Oyprcea Europcea, or European CoAvry ; the shell enveloped, 

 excepting the dorsal ridge, by the mantle of the animal, as 

 in walking. 



1 h. Shell of the same, as when the animal is enclosed. 



2 a. Fu^us Berniciensis. 



3. Eudimentary shell oi Fusus Turtoni. 



4. Egg-bag of the same. 



5. Bulla lignaria. 



Plate XIX. 



1 . Boris planata : has no shell, but the breathing apparatus ex- 

 ternal. 



