4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
considerable care to pick or wash the mud from delicate and brittle interiors. The 
Lincolnshire limestone, such as that at Shiloh Church on the north side of Clinch 
Mountain in the Pressmens Home (T.V.A.) Quadrangle, commonly produces 
quantities of mud when decalcified, and the shells are brittle and sometimes frac- 
tured. They are nevertheless of the finest quality but require great care in 
handling. 
Recognition of silicified brachiopods is generally not difficult because the speci- 
mens are usually weathered into relief on surfaces. The shells, too, often show 
silicious rings or the blue-gray color of chalcedony. When selecting material for 
etching, it is a good plan to look for blocks or take pieces of ledge rock showing 
specimens well scattered throughout the mass and on all sides of the block. 
Inarticulate brachiopods may be prepared by dissolving limestone in acetic 
acid. This is a method described by W. C. Bell (1948). Generally, inarticulates 
are not sufficiently common to give an abundance of specimens from limestone 
pieces. The locality at Pratt Ferry, Ala., is unique in furnishing a great variety 
of inarticulates. Some inarticulates have been prepared by using dilute hydro- 
chloric acid. This is true of much of the cobbly limestone material occurring in 
the lower part of the Edinburg limestone. Paterula, Elliptoglossa, Conotreta, 
occasional linguloids, and Schizambon have been removed from this part of the 
column by hydrochloric acid as well as acetic acid. 
Chemical means can also be used to prepare molds of the interior and exterior 
of brachiopods. This can be successfully accomplished on specimens that are 
not silicified and that are preserved in a silty or fine sandy matrix. It is best to 
apply the acid with a brush or medicine dropper so that the solution of the shell 
can be controlled. It is usually necessary to harden the newly exposed matrix and 
also newly revealed parts so that the mold will not be injured. Numerous speci- 
mens from the Oranda formation were prepared by this treatment. 
Most of the interiors of unsilicified specimens were prepared with needles 
ground to a chisel edge. An excellent utility point may be made by beveling a 
needle of appropriate gage at various angles to the long axis, depending on the 
work to be done. This beveling produces a broad face with sharp edges for 
scraping and also a sharp point for digging. It is best to scrape away matrix 
against the shell rather than dig it away. Careful scraping leaves no unsightly 
scratches. 
A number of interiors were prepared by roasting the specimens in a blast lamp 
and then letting the shell cool. This treatment calcines and softens the shell to 
such an extent that it can be scraped away by a beveled needle. The shell gen- 
erally turns white from the heating and makes a convenient color contrast with 
the matrix. Careful scraping will produce molds of the interior that are quite as 
good as those obtained by dissolving the shell away. The success of a brachiopod 
study depends almost entirely on the information derived from the interior ; con- 
sequently, no pains should be spared to preserve this part. 
ACKNOWLEDGMENTS 
Many friends and interested persons have been of great assistance in the 
preparation of this monograph. Inasmuch as the work originated as a joint un- 
