INTRODUCTION. 



THE following work was undertaken under many disadvantages. 

 The writer did not accompany the Expedition, and, of course, had not 

 an opportunity of observing specimens in their native localities, and in 

 their natural relations. Circumstances relating to food, habits, uses, 

 numbers, and grouping, and other important points which would im- 

 press themselves upon the mind of an observer, and by which the dry 

 details of specific description might be greatly relieved, must, therefore, 

 be wanting here. 



Mr. Joseph P. Couthouy, the able naturalist of the Expedition in 

 this department, made careful and suggestive notes of all interesting 

 species, and, especially, of the new or doubtful species, with the inten- 

 tion of amplifying them after his return. To him they would have 

 spoken volumes ; but he alone could fully understand their import. 

 Up to the time of leaving the Paumotu, or Low Coral Islands, these 

 notes were pretty fully written out in form. On arriving at the 

 Samoa Islands, his health obliged him to separate from the squadron ; 

 and the numerous notes he had subsequently made from day to day 

 were left in an imperfect state. Still, these would have been extremely 

 valuable, especially those relating to the land-shells of the Society, 

 Samoa, and Sandwich Islands. But, unfortunately, repeated searches 

 have failed to discover them among the masses of documents per- 

 taining to the Expedition. 



Mr. Couthouy was also careful to attach marks, or numbers, to all 



