SPECIAL INSTRUCTIONS. 



The shells most wanted for the purposes in view are, in the 

 first place, all the species of the western portion of the continent, 

 the land and freshwater, and especially the marine shells of the 

 Pacific; next the marine shells of the eastern coast, and of the 

 Gulf of Mexico, including the West India Islands ; next the 

 land and 'freshwater univalves generally, with the Cycladidce ; 

 and lastly, as best known, the UnionidcB or Mussels, especially 

 those of the regions west of the Mississippi, and the southern 

 Atlantic and Gulf States. 



Wherever practicable, a full series of the shells of each local- 

 ity, with their animals enclosed, should be preserved in alcohol ; 

 in the case of the smaller species, it will be well to throw in 

 spirit all that can be collected, as much trouble in cleaning will' 

 thereby be saved. Shells with their animals are of much more 

 value for scientific investigations than those without them, and 

 should be carefully sought after. Dead shells, however, or those 

 picked up on the beach or elsewhere, without any animal attached 

 or included, should also be collected in large numbers, even when 

 the same kinds are preserved in alcohol, as showing forms or 

 variations not seen in the other series, or as increasing the aggre- 

 gate of material for the investigation of the species. 



As a general rule, the alcohol used should not be very strong — 

 about fourth proof is the best. The shells, especially the dimi- 

 nutive ones, should be kept in small lots, and not mixed with 

 vertebrates or crustaceans (which require stronger spirit), if it can 

 be avoided. Small bottles, jars, or tin cans may be employed 

 for the purpose. Shells without their animals should be pre- 

 served dry, and not thrown into spirit. 



In packing shells for transportation, care should be taken to 

 have the bottle or box in which they are contained perfectly full, 

 to prevent friction during transportation. The larger ones should 

 be wrapped separately in paper. 



When it is inconvenient to transport shells containing their 

 animals in alcohol, after having been immersed in this fluid, they 

 may be taken out and the animals allowed to dry up. They can 

 at any time be relaxed again for examination by soaking in a 

 solution of strong potassa — although it is best to keep them ia 



