FORMAT OF THE KEYS

New species of harpacticoids are being discovered continually and it is likely that only about half of the species are presently known. It is important, therefore, that these keys are able to accommodate new species with as little disturbance as possible. The traditional dichotomous key is notoriously inefficient in this respect but tabular keys have proved to be more satisfactory and are used in this work. Newell (1970) discusses their advantages and describes how they operate; his methods are used here, with some modifications.

The key consists of two parts; (a) a list of characters used, with a description of the character states and how they are coded for in the key, and (b) the key itself, in which the expression of the character states provides a summary description, as a kind of formula, of the taxon or group of taxa. In the keys to each of the families the primary key group is numbered KGG 1. In this key group some formulae lead direct to a genus or a species, or to a group of species within one genus but others lead to a secondary key group, numbered KGG 100 ………. KGG n00. In some cases formulae in these secondary key groups lead to a tertiary key group, numbered KGG i10 ……… KGG ix0 (where x is a number from 1 to 9). This system of numbering allows for the addition of new KGG if the need arises. It is possible also to extend the system to quaternary key groups if needed.

Despite the flexibility of tabular keys I found it impossible to construct for the Order as a whole a manageable key which led directly to genus or species, but relatively easy to do this for each family. Also I could not construct a simple tabular key to families and have resorted to a dichotomous key adapted from Lang (1948); I am grateful to Hakan Ohlsson’s Boktryckeri for permission to so use it.