PREFACE. 
AN accurate knowledge of the affinities and distribution of the recent 
Shells of New Zealand is a very necessary element in the Geological 
Survey of the country, as it must form the basis of our Tertiary Geology, 
upon the correct decyphering of which many questions of the highest 
interest depend ; such, for instance, as the former distribution of land, 
of ocean currents, and of temperature in the Southern Hemisphere, and 
the true nature of the agencies which have operated in producing the 
Auriferous alluvia or Gold Drifts. 
Shells afford the most reliable data for Paleeontologists ; but before 
the extinct shell fauna can be utilized, the recent shells of the area must 
be thoroughly determined. ‘The preparation of the first Catalogue was 
beset with difficulties, which were explained in the preface to that 
work ; but, as was then anticipated, its publication has led to a vast im- 
provement in our knowledge of the subject. 
The consent of Government was, therefore, readily given to the 
printing of the present work at the public expense, the compilation 
of which has been an entirely gratuitous service on the part of 
Professor Hutton. 
This MANUAL is not, however, merely a new edition of the 
Catalogue by the same Author which was issued by this Department 
in 1873, but it embodies and replaces the following works, all of 
which are now out of print :— 
1. Catalogue of the Marine Mollusca of New Zealand. By 
F. W. Hutton. Wellington, 1873. 
2. Critical List of the Mollusca of New Zealand. By Ed. 
Von Martens. Wellington, 1873. 
