BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [40] 



natural position, attached to each, other by the ligament which holds 

 them together in life. This ligament dries to a very brittle, horny 

 substance. Consequently the shells must be placed in position when 

 fresh, in order to make a success of the operation. After cleaning 

 away the animal matter and thoroughly washing the interior of the 

 shell, it is a good plan to note the locality with a soft lead-pencil upon 

 the shell itself. Then bring the two valves together in their natural 

 position and tie them in that position with a piece of tape or soft twine, 

 which should be allowed to remain until the ligament is thoroughly 

 dry. Specimens prepared in this way are more valuable for exchange 

 and more attractive to the eye than those with which less care has been 

 taken. It is always desirable, however, to have some specimens with 

 separated valves of every bivalve species in the cabinet, in order that 

 the characteristics of the interior may be easily examined. 



Fresh- water bivalves are usually covered with a thin and highly 

 polished, often very elegant, greenish or brownish epidermis. Some- 

 times the shell is so thin that, in drying, the contracting epidermis 

 splits and cracks the shelly portion so that it becomes worthless for 

 the cabinet. This often happens with marine mussels, but is almost 

 characteristic of the thin fresh- water Unionidce. Various methods have 

 been adopted to prevent this unfortunate result. Some collectors have 

 varnished their shells immediately after they were obtained. Others 

 have used sweet oil or other oils in the hope of keeping the epidermis 

 in a soft condition. These applications are all objectionable for one 

 reason or another, as the first endeavor of the collector who desires 

 to make a really scientific collection should be to keep his specimens 

 as nearly as possible in a perfectly natural condition. The most satis- 

 factory substance for application to the shells in question is probably 

 ordinary vaseline, which should be applied in very small quantities, so 

 that the specimen will have no greasy feeling and will absorb the 

 vaseline sufiiciently not to become sticky to the touch. Glycerine, 

 which has been recommended by several collectors, like oil, leaves the 

 surface sticky and offensive to the touch, besides rendering it liable 

 to catch everything in the way of dust with which it may come in 

 contact. 



Very small gastropod shells need not have the soft parts removed. 

 If they are put into a vial of alcohol for twenty-four hours, then taken 

 out and allowed to dry, the soft parts will become desiccated without 

 any offensive odor, and they may be placed in the cabinet without 

 further preparation. It may be noted, however, that if the cabinet 

 contains many such shells, care should be taken to guard against the 

 access of mice and vermin, which are apt to attack them in the absence 

 of something more attractive in the way of food. For those shells 

 which possess an operculum, after the operculum has been dried and 

 the shell cleaned and ready for the cabinet it is customary to insert a 

 little wad of raw cotton, rolled so as to fit the aperture snugly, the 



