74 



Remarks onMollusca and Shells * By Dr Augustus Gould. 



1. On the Zoological Regions. 2. Specific identity of Shells. 



3. Local aspect of Species and characteristic forms oj regions, 



4. Analogous species in co-ordinate regions. 



1. Zoological Regions. 



The doctrine of distinct zoological regions evidently apper- 

 tains to the mollusks, and is well illustrated by them. In 

 nearly every work containing any considerable catalogue of 

 shells, the same species will be found quoted as being found 

 in widely-distant regions, in different oceans, and even on 

 opposite sides of the globe. The many thousand localities 

 carefully noted on the records of the Expedition, go to prove 

 beyond dispute, that no such random or wide-spread distribu- 

 tion exists. The error has arisen from two principal causes. 

 One is, that reliable notes of localities have not been taken. 

 A voyage is made to the Sandwich Islands, and all the shells 

 brought home by the vessel are said to be shells from the 

 Sandwich Islands, though they may have been obtained at 

 California, the Society Islands, New Zealand, and perhaps 

 half-a-dozen other places quite as remote from each other. 

 A sea captain purchases a collection at Calcutta or Valpa- 

 raiso for his friends at home ; and all the shells are marked 

 as denizens of the port where they were purchased, though 

 they might not have lived within thousands of miles. Pur- 

 chased shells cannot be relied on for localities ; for this end 

 a shell must have been found containing the animal, or else 

 dredged, or picked up on the shore, and labelled accordingly. 

 There have been instances where New England shells, which 

 had gone to the west coast of America in the way of ex- 

 change, came back again as Pacific shells. 



2. Identity of Species. 



" Shells are regarded," says Dr Gould, " as specifically 

 identical, which, on careful comparison, are found not to be 

 so. And this is very likely to occur where some one very 

 remarkable peculiarity exists. Thus, a Lutraria from Lower 



* United States Exploring Expedition, vol. xii. 



