Miscellanies. 391 



the surface, it was thrown away, and this crown was all that was saved. 

 Description : — horizontal section of body quadrilateral, with the angles 

 rounded and the sides slightly curved. The crown has two transverse 

 ridges, the summit lines of which are slightly curved ; between the 

 extremities of the ridges on each side is a small tubercular elevation, 

 and a slight elevation borders the anterior and posterior extremities of 

 the crown. 



CI- /• u J f length, 0.94 of an inch. 



Size of body, | bretdth, 0.76 " " 



Length of the summit of the ridges, 0.55 of an inch. Distance of the 

 summits of ridges from each other, 0.42 of an inch. Height of ridges, 

 0.36 of an inch. 



It is without doubt the fifth molar of the left lower jaw of a Tapir, 

 which appears to me to be very near to the one now inhabiting South 

 America, as the form and size of the tooth is nearly the same as in that 

 animal. 



Jackson, La., October 19, 1841. 



7. Preparation of Freshwater Shells for the Caiinet. — We make 

 the following extract from the letter of a distinguished correspondent, 

 whose shells have been in much demand among collectors, and whose 

 mode of preparing them is the result of observation and experience. 



" It is well known that these shells are composed of animal matter 

 and carbonate of lime, thinly laminated. Many of them are more or 

 less covered with mucus, lime, clay and oxide of iron, sometimes indu- 

 rated, so as to require a steel instrument to remove it. Hence the first 

 operation is to remove this extraneous matter by hand-brushes, and then 

 with dilute muriatic acid to remove the free lime and accidental colors ; 

 then, after a thorough rinsing, and as soon as the water has dried from 

 the surface, saturate the shells with the finest spermaceti oil, which 

 should be left on them for several months if convenient, but wiped from 

 them as clean as possible with a woolen cloth before putting them in 

 the cabinet. They will then feel like steatite, and exhibit a transpa- 

 rency and beauty which I could not obtain in any other way. Shells 

 which have once been exposed to the air, without the animal, and have 

 become thoroughly dry, can never be restored to their primitive beauty, 

 because the water of the animal matter in them has evaporated. They 

 become opake, and a slow decomposition, like that of salts, takes place, 

 by the evaporation of the water of crystallization ; but the oil taking 

 the place of the water, as the latter evaporates, increases the transpa- 

 rency of the shell, as it does that of paper, and the superfluous oil may 

 be so effectually removed at the proper time, that the shells will not 

 soil the fingers or smell unpleasantly ; but any considerable exposure 

 to the air. and light will soon injure their appearance." 



