Mollusca of Great Britain. 367 



their organs of respiration they must rank with the ter- 

 restrial Mollusca, are strictly amphibious, living in the 

 clefts of rocks and the under surfaces of stones which are 

 exposed only by the recess of the tide. Their food (at least 

 that of the A.denticulata, the only one of which I have 

 observed the animal,) consists of decaying animal and ve- 

 getable substances. It is curious to observe the strange 

 confusion that has taken place among later authors as to 

 the real habitat of this class. Montagu and Draparnaud 

 respectively assigned to their Valuta denticulata and Auricula 

 myosotis a place among the marine and terrestrial Mollusca : 

 the one from having observed the shells with their animals 

 on Alga at high- water mark on the Plymouth coast; and 

 the other on dead and decaying wood on the shores of the 

 Mediterranean. Baron Ferussac indeed was perfectly 

 aware of their peculiar organization, but errs in saying 

 that they have the power of going out of the water. The 

 last-mentioned author has arranged them under his Gehy- 

 drophiles, a very interesting sub-order of the pulmoniferous 

 Mollusca, but a much too extensive one, since it embraces 

 the Valuta tornatilis. Turbo unidentatus, plicatus, ^c. of Mon- 

 tagu ; all which, from opportunities I have had of examining 

 their animals, I am perfectly assured do not agree with the 

 present division, having a very different respiratory system 

 and a truly marine habitat. 



The want of the internal spiral septa of the shells first 

 noticed by Montagu is very curious. 



1. Denticulata. 



Animal griseo-purpurascens. Tentacula brevia, annulata. 

 Proboscis elongatus. 



Testa oblonga, subventricosa, fragilis, glabra, purpureo- 

 voL. XVI. 3 B fuscescens. 



