Scientific names established in accordance with the principles of binomial nomenclature consist of two parts: the _generic_ (or _genus_) name and the _trivial_ name. These names are commonly derived from Greek or Latin words which are usually descriptive of the organism or fossil being named. They may, however, be derived from the names of people or places, and in such instances the names are always Latinized. Greek or Latin is used because they are “dead” languages and not subject to change. They are also “international” languages in that scientists all over the world can use the same names regardless of what language they write in. The system of binomial nomenclature has led to the development of the science of _taxonomy_, the systematic classification and naming of plants and animals according to their relationships. THE UNITS OF CLASSIFICATION The world of organic life has been divided into the plant and animal kingdoms. These kingdoms have been further divided into larger divisions called _phyla_ (from the Greek word _phylon_, a race). Each phylum is composed of organisms with certain characteristics in common. For example, all animals with a spinal cord (or notochord) are assigned to the phylum Chordata. The phylum is reduced to smaller divisions called _classes_, classes are divided into _orders_, orders into _families_, families into _genera_, and each genus is divided into still smaller units called _species_. A species may be further reduced to subspecies, varieties, or other subspecific categories, but these need not concern us in a publication of this nature. The following table illustrates the use of binomial nomenclature in the classification of man, a clam, and a dog. Unit Man Dog Clam Kingdom Animalia Animalia Animalia Phylum Chordata Chordata Mollusca Class Mammalia Mammalia Pelecypoda Order Primates Carnivora Eulamellibranchia Family Hominidae Canidae Veneridae Genus _Homo_ _Canis_ _Venus_ Species _sapiens_ _familiaris_ _mercenaria_ The generic name and the trivial name constitute the _scientific name_ of a species and according to this system of classification the scientific name of all living men is _Homo sapiens_. It is obvious that there are many variations among individual men, but all men have certain general characteristics in common and are therefore placed in the same species. In a scientific name, the generic name is always started with a capital letter and the trivial name with a small letter. Both names must be italicized or underlined. The name of the author (the person who first described the fossil) usually appears following the scientific name. The date of the scientific publication containing the original description of the fossil is often placed after the author. For example: _Turrilites worthensis_ Adkins and Winton 1920