known or earliest studied. Thus all lampreys constitute the family Petromyzonidæ.
An order may contain one or more families. An order is a division of a larger group; a family, an assemblage of related smaller groups. Intermediate groups are often recognized by the prefixes sub or super. A subgenus is a division of a genus. A subspecies is a geographic race or variation within a species; a superfamily, a group of allied families.
Binominal nomenclature, or the use of the name of genus and species as a scientific name was introduced into science as a systematic method by Linnæus. In the tenth edition of his 'Systema Naturæ' published in 1758, this method was first consistently applied to animals. By common consent, the scientific naming of animals begins with this year, and no account is taken of names given earlier, as these are, except by accident, never binomial. Those authors who wrote before the adoption of the rule of binomials and those who neglected it are alike ruled out of court. The idea of genus and species was well understood before Linnaeus, but the specific name used was not one word but a descriptive phrase, and this phrase was changed at the whim of the different authors. Examples of such names are these of the West Indian trunk-fish, or Cuckold: Ostracion tricornis of Linnæus. Lister refers to a specimen in 1686 as Piscis triangularis capiti cormitis cui e media cauda cutanea oculeus longus erigitus. This Aretdi alters in 1738 to Ostracion triangulatus aculeis duobus in capiti et unico longioro superne ad caudam. This is more accurately descriptive and it recognizes the existence of a generic type, Ostracion, or trunk fish, to cover all similar fishes. French writers transformed this into various phrases beginning: Coffre triangulaire a trois cornes or some similar descriptive epithet, and in English or German it was likely to wander still farther from the original. But Linnaeus condenses it all in the word tricornis, which although not fully descriptive, is still a name which all future observers can use and recognize.
It is true that common consent fixes the date of the beginning of nomenclature at 1758, but to this there are many exceptions. Some writers date genera from the first recognition of a collective idea under a single name. Others follow even species back through the occasional accidental binomials. Most British writers have chosen the final and completed edition of the 'Systema Naturæ,' the last work of Linnæus' hand in 1766, in preference to the earlier volume. But all things considered, justice and convenience alike seem best served by the use of the edition of 1758.
Synonymy is the record of the names applied at different times to the same group or species. With characteristic pungency Dr. Coues defines synonymy as 'a burden and a disgrace to science.' It has been found that the only way to prevent utter confusion is to use for each
