I" 



PREFACE. 



The principal object of the present Catalogue is to give a 

 complete List of the Free Air-Breathing Mollusca {Mol- 

 lusca Pulmonata), with descriptions of all the genera and 

 species known to exist, indicating at the same time, by 

 a B.M. in the margin, those contained in the British 

 Museum. 



The descriptions of the species of Shells belonging to 

 these animals are by Dr. Louis Pfeiffer of Cassel, so 

 well known for his attention to the Shells of Terrestrial 

 Mollusca. The account of the animals and their arrange- 

 ment has been brought up to the present state of the 

 science. 



JOHN EDWARD GRAY. 



British Museum, 

 29 March, 1855. 



