BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [14] 



In gastropods the form of the aperture is one of the most impor- 

 tant features, but one that is most frequently imperfect in si)ecimeus col- 

 lected from hard rocks. In. species with long canals and expanded 

 outer lips, carefully save every fragment of these parts. 



Siliceous fossils. — Fossils of a siliceous nature, i^artially weathered out 

 of limestone, should be gathered in bulk, to be treated in tlie Museum 

 with muriatic acid. Material which will bear this treatment is readily 

 tested with a pocketknife. If the knife does not scratch the fossil, but 

 leaves a black mark, it will be well to make an experiment. Of course, 

 where the fossils are in cherts or are more or less surrounded with 

 amorphous silica nothing can be done to free them. Limestone with 

 fossils changed into iron pyrite or of a carbonaceous or phosphatic com- 

 position can also be submitted to the acid process of developing. The 

 structure and young stages of graptolites, linguloids, goniatites, etc., 

 are sometimes only obtained by this method. 



Fossiiiferous shales. — Where fossils are found free and abundantly 

 weathered out of clay or shale, it is always advisable to take a small 

 quantity of the weathered shale and wash in a pan until the water is 

 no longer colored by the residuum. If this is found to contain an abun- 

 dance of fossils, a box of clay unwashed should be gathered. The 

 object of such collecting is to obtain the young stages of mature forms 

 and also microscopic organisms, such as ostracods, bryozoa, etc. 



Calcareous fossils. — Fossils of this nature taken from shale banks and 

 much covered with firmly adhering shale, if otherwise good and solid, 

 should not be thrown away, since many of these can be cleaned with 

 caustic potash. This is particularly true of corals and the interior of 

 brachiopods. 



Fossil-yielding marls. — Marls having an abundance of small fossils, 

 which frequently occur in Tertiary deposits, should be dug ux> and 

 shoveled into barrels or boxes, to be picked over in the laboratory. 

 This plan, however, is only feasible when the fossils are reasonably 

 hard. Mr. T. W. Stanton suggests the following plan of operation : 



In sandy marls like those of the Cretaceous in the Southern States the animal mat- 

 ter has nearly all been removed from the more delicate shells, leaving them in a very 

 soft con(?ition that will not permit rough handling. In such cases the marl should 

 be carefully dug uj) and the pieces showing edges or surfaces of fossils trimmed with 

 knife and hammer to a convenient size for packing. When the marl is compact and 

 not too wet good results have been obtained by blasting, using au inch and a half 

 auger with a shank about 4 feet long for making the hole. No attempt should be 

 made to expose the fossils in the field nor to free them from the matrix, as they would 

 then be broken in transit. It is a good plan to have at hand a hot solution of com- 

 mon furniture glue and to apply a coat of it to all exposed surfaces of shells, other- 

 wise they are likely to crack and fall to pieces on drying. The glue is to be used in 

 preference to other hardening materials, because it can be easily washed off with a 

 wet sponge and does not interfere with the subsequent cleaning of the fossils. Col- 

 lections of this kind should be packed in cotton or other soft material in small boxes, 

 which may then be packed in a larger box. If this is not done the fossils are likely 

 to be crushed and ruined by their own weight. 



