INTRODUCTION 5 



TECHNICAL TERMS. We started this book with the idea of using plain English as much as 

 possible. That meant avoiding technical terms dear to the paleontologist's heart but puzzling 

 to everybody else. So we used "tail shield" instead of "pygidium," "head shield" instead 

 of "cephalon" for the trilobites. But we soon found out that we would have to use a minimum 

 number of technical terms for which we could not find a simpler word. Technical terms are 

 explained at the proper place in the text and the index at the end of the book lists them 

 alphabetically. Learning tnese technical terms will be easier than it seems and it will help 

 you when you go on from this book to more specialized ones. After all, no one learns to 

 drive a car without absorbing a few technical terms in the process. Everybody knows what 

 a steering wheel, choke, accelerator, and radiators are. So with fossils; they have special 

 names for their parts too. 



NAME CHANGES. Don't be surprised if you find a fossil called by one name in this book 

 and by another name elsewhere. Name changes are the rule rather than the exception in 

 paleontology. In several cases we have given the names used in older publications for the 

 benefit of those who might consult them, but we have not listed them all by any means. You 

 might well ask why paleontologists, people who study fossils, change their minds about names 

 so often. There is a reason for it which can best be illustrated by an example. 



In the early days, comparatively few species of straight cephalopods were known and 

 they were all called Orthoc e ras (from the Greek ortho, straight and ceras, horn; because 

 the shells are horn-shaped and straight. ) Before long, the list of species grew to unmanage- 

 able size. Then it was found that these straight shells were very different from each other 

 inside though they looked pretty much alike on the outside. So the genus Orthoceras was 

 split up into a number of others, each genus recognizable by special characters and with 

 fewer species in each. It is just as if we had lumped all South Americans together at first and 

 then decided to separate the Chileans from the Brazilians, and the Colombians from the 

 Venezuelans. There is an advantage to distinguishing these people according to the country 

 they come from instead of lumping them all together. 



In this book we have given the latest correct name known to us for each genus. The 

 older names are given in parentheses after the one now in use. 



CLEANING AND PREPARATION. Fossils brought in from the field may still have a lot 

 of rock clinging to them and obscuring their detail. Much of this excess rock can be removed 

 with hammer and chisel, large chisels for the coarser work, smaller and smaller ones for the 

 finer detail. Mounted needles can be used for very fine detail. Much labor may be saved 

 by using power tools, both grinding and chipping, for removing surplus rock from fossils. 



If a fossil is broken in the field or during preparation it can be mended neatly with Duco 

 household cement or a plastic cement of the same nature. Very fragile specimens may be 

 backed with plaster of Paris or liquid plastic. If the surface of the fossil starts to crumble, 

 it can be protected with a thin coat of dilute liquid celluloid. Clear nail polish is a handy form 

 of this. Shellac or varnish should not be used for this purpose as they are hard to remove 

 from fossils and they check or crack sooner than liquid celluloid. 



If the fossil is preserved as a mold, you may want to make a cast of it, to see what the 

 fossil looked like in life. If the mold has no undercuts, plaster of Paris may be used for this 

 purpose. If it has undercuts (and most molds do) liquid rubber should be used for making the 

 cast. Dental wax can also be used as it is much more flexible in relieving from a mold than 

 plaster of Paris. 



Using plaster of Paris is simple but you should not attempt it until you are thoroughly 

 familiar with the steps involved. These cannot be described in detail here but a few words of 

 caution may help. Plaster should be mixed where it won't matter too much if you make a 

 mess; it can be a pretty messy business, especially on your first try. Plaster sticks to 

 things, including fossils, so before you pour plaster on a good specimen, make sure that 

 the specimen is well greased; ordinary motor or lubricating oil is good for this. 



