114 



procedure i.s recoiniiiended : " Paheozoic fos.silit'eroiis elays, 

 which are to be washed for small and young fossils, should 

 be fii'st dried in an oven or in tlie sun, and then well soaked 

 in water for a day or more before washing. A deep pan or 

 bucket serves well for this ])uri)()se, using- the hands to stir 

 the mass around, but do not get too much mud in suspen- 

 sion, since in poiu'ing off the muddy water many of the 



smaller organisms are liable to be carried away 



After the washed earth has been dried, it should be sifted, to 

 facilitate ])icking, into three grades, using sieves of 6, 18, and 

 8S meshes to the inch. The coarser material can be assorted 

 with the unaided eye, but the finer grades will have to be 

 selected under a low-power lens. A moistened camers-hair 

 brush is the best tool with which to pick uj) these smaller 

 organisms. If the brush is held in the end of a small \'ial, a 

 twirl of the fingers will readily remove the attached fossil."* 



Highly fossiliferous shales, such as that of the Demissa 

 bed, ma}' be disintegi-ated by drying them well in an oven 

 and then soaking in water until they cruml)le. Repeated 

 drying and soaking Avih reduce most of the material to clay, 

 after wdiich the fine mud is to be washed away. The final 

 process consists of boiling the material in a dish for about 

 half an houi-. frecpiently changing the water, until no more 

 mud appears. 



Washing the Clay for Microscopic Organisms. The fol- 

 lowing method is recommended for obtaining microscopic 

 organisms from the clays resulting from the disintegration 

 of the shales : 



"In preparing most of the samples of clay, we would put 

 about one ounce of the material and the same amount of 

 common washing soda into a druggist's two-quart, clear- 

 glass packing bottle, not over one-fourth filled with ^^-ater, 

 and let it remain twelve to twenty-four hours, frecpiently 

 shaking the bottle, so as to thoroughly break u]j xhe chiy. 

 ]\ow fill the l)ottlewith water, and after twenty-five minutes 



* Schuchert, Bull. 39, U. S. Nat. Mus. Part K., p. 20. 



