286 ON COLLECTING SHELLS. 



the outside. Let the shells stand until all moisture is dried off 

 the outside, and then wrap them close in an old newspaper, to 

 prevent gaping by the contraction of the ligament. Smaller 

 ones may be nested in larger ones on long journeys, where space 

 is desirable and must be economized. But never do so if you 

 can avoid it. It frequently occurs that the shells of Unionidse, 

 Strepomatidae, and Limnseidae are stained with ferruginous and 

 other matters that no amount of washing will remove. If such 

 shells are immersed for a few moments in the oxalic acid solution, 

 these stains will readily wash off", and a judicious use of the 

 acid does not harm the shell in the least. If it is desirable 

 to remove these stains from the Unionidse, they should be dropped 

 into the acid immediately after washing and before scalding out 

 the animal, the presence of which prevents the acid from coming 

 in contact with the nacre of the shell, which it will slightly dim 

 if the shell remains in it for too long a time. It is often the case 

 among the southern shells that these stains have so obscured the 

 really characteristic markings of the shells as to have made it 

 one of the chief causes of so much synonymy. If dead shells 

 must be taken or muskrat shell-heaps explored, which is some- 

 times the case, a judicious use of the acetic acid will remove 

 stains, and in many cases fairly well restore the original appear- 

 ance of the nacre. 



The black and dirtj^ univalves which are so generally received 

 in exchange, and also dirty Unionidse, may be perfectly cleaned 

 by a judicious use of these acids. But while thej^ are to the 

 careful student collector an inestimable boon, a careless or inju- 

 dicious use of them will ruin every shell so treated. 



Where the Strepomatidae are collected in alcohol or any preser- 

 vative solution in quantity, they may be subjected to the cleaning 

 process whenever opportunity offers. It will generally only be 

 necessary to immerse those having the worst stains in the acid 

 for a few moments, and then wash and rinse them thoroughly. 



In operculated species, the operculum, detached from the animal 

 by a sharp knife, should be carefully preserved. A little cotton 

 can be inserted into the aperture and upon this, the operculum, 

 in its natural position, may be fixed with mucilage. 



Many Uniones and univalves are much improved and given the 

 appearance they have when in water, or when wet Iby rubbing 

 them with a clean sponge, on which are a few drops of boiled 

 linseed oil. "Woolly" shells or those with a soft epidermis 

 may be excluded from this list. 



Many of the Unionidse also have a very highly polished 

 epidermis, and when clean look as well dry as wet. The use of 

 oil is a great improvement to some species, and it preserves all 

 fresh-water shells ; but it must be kept off of land species. The 

 Anodontas and thin-shelled Unios sometimes crack when dry. 

 This ditBculty may be avoided by dipping fresh splebimens into 



