Best practice guide for using a Lucid key

We have provided an easy-access route to the key which should hopefully satisfy the great majority of users. This is by way of an interface that enables the user to choose 'subsets' of features – for example by limiting to shell characters only. Other options include choosing a taxonomic group to start with (assuming that you are confident that your specimen is a member of that chosen group) (e.g., Gastropoda or Bivalvia, or a particular family), or on the basis of habitat, location, and pest or conservation status.

This gateway can be skipped, in which case the full key will be entered, showing all available features. However, we only recommend this option for experienced users.

General use of a Lucid key

During an identification session, Lucid allows you to choose any question (i.e. a 'feature' and its states) in its list at any time, but "stepping" through the key in a structured and sensible way will make your task of identification easier. 'Features may be morphological characters, habitat, geographic details or other information. 'Items' are the taxa (species, genera and families).

Features (characters) and their notes

In Lucid, features are the characters and other information (e.g., habitat, distribution) used in the key to distinguish 'items' (i.e., taxa such as species, genera etc.).

You can select more than one state for a given feature, and you can also scroll back to unselect features if you think you may have made an error.

Ensure that you are familiar with the notes provided for each feature, as these provide guidance on its utilisation as well as potential pitfalls.

Familiarity with the specimen

First, become familiar with the characteristics of the specimen you wish to identify. Briefly reviewing these before you start will make it easier to proceed through the identification.

Note and use distinctive features

In any key, some taxa may possess particularly distinctive features. Use of these may allow the taxon to be keyed out in very few steps. At the very least, starting with particularly distinctive or striking features for the first character states selected may quickly reduce the list of Entities Remaining.

Answer easy features first

Browse the list of Features Available and address easy features first. The principles of a standard printed key consisting of dichotomous choices and in which the couplets must be answered in a pre-set order, are very familiar to most key users who often automatically apply these principles to an interactive key. Although Lucid lists the features of a key in an initial sequence in the opening window, this does not mean that the features must be selected in that order. You can select any feature from any position in the list.

Most Lucid keys will have a wide variety of features, ranging from those dealing with obvious and simple features to those dealing with features that are minute, obscure or difficult to interpret. Always start by browsing the list of Features Available for obvious features that you can quite quickly answer, as opposed to needlessly meeting obstacles with the first listed feature. Lucid is designed to overcome problems associated with difficult and obscure features.

Choosing multiple states

Always choose multiple states (more than one state of a feature) if you are uncertain which state is the correct one to choose for a particular specimen. Lucid is designed to allow you to choose as many states as you require from any one feature. Within the program's logic, these states will be connected by an "or" link. This will cause Lucid to search for all taxa with any of the states you select. As a general rule, if you are unsure which of two or more states your specimen has, then choose them all: that way, you can be sure that your target taxon will remain in Entities Remaining.

Finding the best feature to address next

When you have dealt with all the obvious features, use Lucid's "Best" function to suggest the best remaining feature. The Lucid Player has two "Best" modes, Find Best and Sort Best.

Find Best: In the Lucid Player, clicking the Best button will cause the Player to move to and open the best available feature. Next Best and Previous Best buttons on the toolbar allow navigation through the Features list, if you have difficulty in addressing the first feature nominated. If the list of entities in Entities Remaining changes after choosing a feature as suggested by Best, you should click the Best button again to recalculate the next best feature to address.

Sort Best: Sort Best will reorder the Features Available list so that features are sorted from most to least appropriate. After a Sort Best, scan the top of the list for features that you can answer most easily. Note that Sort Best only works using List View, as a tree representation (Tree View) of features cannot be sorted.

What if no taxa remain?

This will happen sooner or later in one of your Lucid sessions. If no taxa are listed in the Entities Remaining window, it simply means that no taxa in the database match the selection of states you have made. Several explanations are possible, but some of the most common are:

Whichever of the above situations is suspected, you must carefully review your chosen features and determine which ones you are uncertain about. Try unselecting uncertain states one by one to reveal their respective effects on your identification process. One or more taxa may move back into the 'Entities Remaining' window. In difficult cases, you may need to resort to some trial and error with the key, adding or deleting states progressively to try to find the best matching taxon.

What if several taxa remain?

Never assume that you will always end up with one taxon remaining. Some taxa in this key are hard to differentiate, especially if difficult or obscure features (e.g., anatomy) are not utilised in the identification. Sometimes, after you have addressed all the features, you may have a few taxa remaining instead of just one. However, even in these instances you may still be much closer to an identification than you otherwise might have been. However, if you are experiencing issues with identification (particularly in the presence of too many remaining taxa) checking the illustrations of the species remaining and their geographic ranges and other associated information available in Fact Sheets may be helpful. In potential circumstances where such information does not fit your specimen, this could be due to the user having inappropriately scored one or more characters (i.e., Features), or when an undescribed species or an exotic species not included in the key are encountered (see below for suggestions on how to deal with this).

Checking the result

Once you have made a preliminary identification, check the other information (such as Fact Sheets, notes, descriptions and images) provided for the taxon to help to confirm the identification. It is possible that errors were made during scoring, or you may have a taxon that is not in the key. In both these cases, the key may have provided you with the wrong name. The information on the associated Fact Sheet should give you a good indication as to whether the answer is correct.

What does 'remaining entities' mean?

When using this key, you may notice that the number of remaining entities does not necessarily correspond to the exact number of species remaining – this is because entities encompass all taxonomic groups. As such, if only a single species remains as a result of your scoring, it may still show three remaining entities, as these encompass the ranks of the taxonomic hierarchy (family, genus, species) within which the species has been classified.

Setting key preferences

Several options are available in the 'Set Key Preferences' menu.

These are:

Key Functions

Retain selected subsets on restart – The default setting is to have the last subset chosen remembered when you restart the key. If you wish to start with no subset chosen, turn this setting off.

Why doesn't every genus have a fact sheet?

Fact Sheets for genus-level groups are not provided for 'monotypic' genera (i.e., genera containing only one species), nor are they provided for genera with only one representative species in the key (i.e, only one species found in Australian freshwater environments). This is because most or all of the relevant information about monotypic genera will be contained by their representative species Fact Sheet. For genus-level groups that may have many species represented in other environments, whether in Australia or overseas, Fact Sheets have not been provided as these are not considered relevant to this resource.

Natural descriptions

Although fact sheets to species contain diagnostic features, such features can also be obtained through the 'description' icon associated with every taxon in the interactive key. Please note that while we have tried to address language issues in these descriptions, they are automatically generated based on the scoring associated with each taxon. Therefore, the language may be somewhat repetitive or at times unwieldy in these descriptions, especially when multiple states are involved.

Anatomical characters

Some anatomical features of all taxa are included. While some of these are easily accessible, others will require dissection to observe. As many species are small, we recommend Geiger et al. (2007) as a best practice guide for preparing, storing, and dissecting the smaller species. This paper also provides detailed information on how to mount and examine the radula, clean shells, store specimens, and other useful techniques The key contains detailed anatomical information on members of the Tateidae. This is because many species of that family have been described using, in part, anatomical characters. In some cases, those species are therefore best separated using certain features of the anatomy. We have included these data in the key, but recommend their use only by experienced users that are prepared to carefully undertake micro-dissection.

Exotic species

Several non-native species, falling into the following five categories, are included in this key:

Undescribed species

With two exceptions, the key only deals with described species. There are many undescribed species known to us that, hopefully, will be formally described and added to the key in the future. Most of these occur in caves, or in groundwater, although a number of new surface species are also known, mainly from parts of Tasmania, Victoria and Queensland. If you suspect that you have an undescribed species, you can contact us for confirmation (see contact details for authors below).

Homepage display issues

Please note that the homepage design was originally intended for PC. While we have tried to cater for various mobile formats, we emphasise that we have not tested the homepage comprehensively across all operating systems and resolutions for mobile devices. Therefore, there may be instances where the configuration of graphic elements may appear arbitrarily or there is overlap amongst text and graphics. We intend to address these issues by the next iteration of this resource, and we also plan to release a mobile app version in the future.

Limitations, error reporting and new records

As with any resource such as this, there are undoubtedly some errors and sometimes, as noted above, exceptional specimens will not key out correctly. Distribution maps are based mainly on records from the Australian Museum, Sydney. We would have liked to have investigated other state museum records, but unfortunately did not have the time or resources to do so in detail. Consequently, the maps should be used as a guide only. We have not included maps for introduced taxa except in a few cases where they are well-established and widespread. We welcome reports of errors, new records, or new observations. New records and observations should be accompanied by photographs or specimens for confirmation.

Our contact by email is, and by mail is c/o Dr W. Ponder, Australian Museum, 1 William Street, Sydney, NSW 2010.


Geiger, D. L., Marshall, B. A., Ponder, W. F., Sasaki, T. & Warén, A. (2007). Techniques for collecting, handling, preparing, storing and examining small molluscan specimens. Molluscan Research 27: 1-50.