450 MICHIGAN SURVEY, 1905. 



should be increased. Twenty-four hours, however, in the alcohol is all that 

 is necessary. Then they can be dried in the air without leaving any of- 

 fensive odor. Either before or after drying they can be cleaned by putting 

 them in a bottle with some fine, clean sand and shaking them together until 

 all the dirt has been removed by the sand. 



Specimens of land snails desired for anatomical purposes should be drowned 

 before being put into the alcohol or formaldehyde, otherwise they retire as 

 far as jDossible within the shell and are more difficult to dissect in this con- 

 tracted condition. By drowning, they die fully extended and can then be 

 put into the preservative. It takes about a day to kill a snail in this way. 

 The alcohol at first should be greatly diluted, not stronger than 25 per cent., 

 after a day or two the specimens should be removed to 50 per cent, alcohol, 

 and later to the undiluted. Formaldehyde, 2 per cent, dilution, is an ad- 

 mirable preservative for material of this kind. It should not, however, be 

 used when it is desired to keep the shells as specimens as it destroys them 

 if left in it any length of time. 



With the exception of the larger species of Planorhis, which are more 

 easily cleaned by boiling, it is practically immaterial whether the fluviatile 

 univalves are boiled or put directly into diluted alcohol. In either case 

 there is no difficulty in extracting the animals. The minute species are 

 treated the same as the small land shells. In the operculate species, it is 

 desirable to retain the opercula of, at least, part of the specimens. While 

 it adds to the labor, it increases the value of the specimen, if it is always 

 clone. These are easily removed from the animal and, after being cleaned, 

 should be put inside the shell and the aperture plugged with cotton. All 

 the foreign matter both inside and outside of the shell should be removed 

 by thorough washing. All the water species are apt to be more or less in- 

 crusted with deposits of lime or oxide of iron. These can be removed by 

 immersing them in oxalic acid. Care should be taken not to prolong the 

 operation, or the texture of the shell may be injured. Elbow grease is the 

 most effective agent for making good specimens. When that fails, use the 

 acid. The Ancyli are always more or less coated in this way, and can easily 

 be cleaned by floating them for a few seconds on the acid, upside down, 

 and then gently brushing them off with a soft brush while held on the tip 

 of the finger. 



The larger bivalves should be well washed and, if necessar}^, scraped off 

 with the knife as soon as taken, care being taken not to injure the epidermis. 



They can be boiled, if desired, when the shells will open and the animals 

 easily removed. But as a rule it is more convenient to cut the muscles, 

 which hold the valves together, with a thin bladed knife and scrape the 

 animal out. Care should be taken not to break the edge of the fragile species 

 when inserting the knife. All traces of animal matter should be removed, 

 and after a thorough washing the valves tied together with a string until 

 thoroughly dried. Never use colored twine for this purpose, as it is apt 

 to stain the shells. Any surface incrustation can be removed either with 

 oxalic or muriatic acid. The latter is more convenient for the larger species, 

 and can be applied with a small brush. It does not bite the fingers, so that 

 it can be used freely. Care, however, must be exercised in using it and the 

 specimens frequently washed, lest damage be done to the shell. The smaller 

 bivalves, the Sphceria and Pisidia, are best treated by putting into diluted 

 alcohol for a day or two and then drying them. If left too long the shells 

 are apt to open, which interferes with the looks of the specimens. 



The larger species of Sphcerium are better with the animal removed. This 



