128 S ABEL J. A. 



rather rare. The denomination of the tribe is 

 taken from the principal constituent of their edi- 

 fices_, S-dh\x\umyJine gravel or sand. 



It may possibly be remarked that in the preceding 

 description of the genera of shells^ no mention has 

 been made by name, of the systems and opinions 

 of either former or cotemporary writers on the sub- 

 ject. This omission has not arisen from any want 

 of respect to the literary labours of those who with 

 great research and skill have brought the science 

 of Conchology to its present state^ or of those who^ 

 like the author, have availed themselves largely of 

 the written documents furnished by works m the 

 German, French, and Latin languages which have 

 not been translated into our own. The names of 

 Testaceological writers, and the titles of their 

 books, with short notices on some, will be given 

 in another place : but it has appeared to be one 

 great source of the uncertainty and confusion at- 

 tending this branch of study, that the beginner had 

 not only to learn a system, but to select one from 



