1867.] 193 [Annual Ueport. 



geographical distribution, and on other important points. 

 Before the voyage was completed he left the expedition, 

 but the notes and collections were sent to Washington. 

 The former Avere unaccountably lost, and no trace of them 

 was found. The collections, when they came into the hands 

 of the Navy Department, were re])acked by incompetent 

 hands, the arrangement of them disturbed, labels in many 

 cases lost, and the whole thrown more or less into con- 

 fusion. Dr. Gould was called upon to save the wreck, but 

 in accepting the task was obliged to submit to various 

 r.rbitrary restrictions, and to leave undone many things he 

 deemed of much importance. Fully ajipreciating the value 

 of a knowledge of the internal structure of the animals, and 

 knowing too well the folly of attem])ting to find all the char- 

 acters for a zoological description in tlie shell alone, he ex- 

 presses his regret at the outset that full dissections and 

 delineations of the internal features had not been directed 

 or allowed. This was all the more to be regretted, since 

 there was a great abundance of material for the required in- 

 vestigations. 



Agreeably to his instructions, the work is almost wholly 

 confined to generic and specific descriptions. In the intro- 

 duction, however, he presents several generalizations of im- 

 portance. By a careful comparison, he shows that Molhisca 

 are confined generally to definite districts or areas. Descrij)- 

 tive writers have frequently given support to opposite vicAvs 

 and have fallen into error from not having taken proper care 

 to ascertain the locality from which certain species came, a de- 

 termination which is now considered of such prime impor- 

 tance. Shells purchased in the Hawaiian Islands are de- 

 scribed as denizens of these islands, notwithstanding they 

 may have been carried there from far off jilaces. New Eng- 

 land shells which have been sent to the western coast of 

 America, have been known to come back in the Avay of ex- 

 changes, as natives of the Pacific shores. Errors have also 

 been committed by attempting to decide the identity of spe- 

 cies from distant places, by the shell alone, when observa- 

 tion has proved this in many cases impossible. When such, 

 and other sources of error, are eliminated, the number of 



PROCEEDINGS B. S. N. H. — VOL. XI. 13 AUOTTST, 1867. 



