8io NORTH AMERICAN INDEX FOSSILS. 



When fossils are broken, the pieces should first be thoroughly 

 cleaned, and then cemented with liquid glue. To dry, place the 

 specimen on a " sand bath " or box of fine sand so that the parts 

 are supported in the position in which they are to be cemented. 

 Supports of clay or plastolin may also be used. Fossil shells pre- 

 served in clay, often adhere to the matrix exposing only the inner 

 surface. In such a case dental wax may be melted into the fossil, 

 and this burned in thoroughly by the use of a blowpipe. After 

 cooling, the shell, now filled with the hard wax, will readily separate 

 from the clay or the clay may be dug and washed away. Excellent 

 results have been obtained from this method by the Maryland sur- 

 vey in the study of the Tertiary fauna of the coastal plain. 



Loose sands or weathered shales are best treated by the use of 

 sieves of various sizes of mesh. The sieve with the largest mesh 

 is placed at the top of the series and the finest at the bottom. The 

 material may be sifted dry, but it is often better to play a stream 

 of water on the topmost sieve on which the material is placed. The 

 finest material which passes through the bottom sieve, and the water 

 is caught in a dish placed below the sieves. The sieves are kept 

 in constant motion as one mass (the sieves obtainable fit into one 

 another sufficiently for rigidity) and as a result the material will 

 be found sorted according to sizes. The fossils may then be picked 

 out by means of a pair of pointed pincers or a moistened camel 

 hair brush. The material caught in the dish below may be ex- 

 amined after gently pouring off the water. Clean water should be 

 used, otherwise foreign particles may be included. Schuchert sug- 

 gests that the mud to be washed for fine organisms should first be 

 thoroughly dried in an oven or the sun, and then well soaked in 

 water for a day or more before washing. He advocates sieves of 

 6, i8 and 38 meshes to the inch for the separation. 



Fossils may be removed from shales by alternately soaking the 

 mass in water and heating in an oven until it is entirely disin- 

 tegrated. Running water applied to this material will wash away 

 the mud, and the remaining material with its enclosed fossils may 

 be subjected to boiling over a brisk fire *' for about half an hour, 

 the boiling being continued with occasional changes of water till 

 little or no mud appears." 



