SHELL-BEARING BRITISH MOLLUSCA, IX 



Plate XV. 



The animals of Turritella, 1-3, and Caecum, 6, 7, are not unlike, 

 although the shells are so different ; eyes at the base of the tentacles, 

 a short foot, and horny operculum. The somewhat similar animal of 

 Aporrkais, 4, 5, is brilliantly coloured with gold and red. Cerithium, 

 8-10, differs from Cerit/dopsis, 11-15, more in regard to the animal 

 than the shell ; the latter animal has a retractile proboscis, and its 

 operculum is not spiral. 



Plate XVI. 



Chemnitzia, 1-11, and Truncatella, 12, together with Sty lifer, 

 Eulima, and Odostomia, form the family of Pyramidellidce. Notwith- 

 standing the difference in the shells, the animals are very similar, 

 having a retractile proboscis, and eyes immersed at the base of their 

 tentacles. 



The animal of Natica, 13-19, has a lobe on the upper part of 

 the foot, reflected over the shell in front, and another lobe behind. 

 The shells of Laminaria, 23, 24, are completely enveloped in similar 

 lobes, 



Plate XVII. 



The shells of Odostomia are known by a fold in the inner lip of the 

 aperture, 



Plate XVIII. 



Two Tritons, 1, 2, are admitted for the first time as British, on what 

 we consider fair evidence, although only two or three specimens have 

 been taken off Guernsey. One of T. nodiferus was incrusted by a 

 truly British Lepralia. Murex, 3, is now familiar as an aquarian, as 

 well as Purpura, 5. A milky secretion found in the head turns purple 

 when exposed, and gives the celebrated purple dye. Buccinum, 7-13, 

 includes the common " Whelk," 8. Fusus Berniciensis, 14, is among 

 the rarest and most beautiful of our British shells. 



Plate XIX. 



Nassa reticulata, 3, is a favourite inhabitant of the tank ; it burrows 

 in search of food among the pebbles, elevating its siphon above the 



b 



