Key Features of Mussel Identification
Easy and accurate use of this handbook relies on a familiarity with mussel shell features. The links below open images and descriptions of the most important of these, illustrating them with typical examples from metro area specimens. Most of our taxa are relatively easy to identify by careful use of these external features alone; for problematic taxa, a key to area species has been provided by the New Jersey Endangered and Nongame Species Program.
To aid in the conservation of living mussels, only the shell features are illustrated. Use of the soft tissues and internal organs, often used for accurate determination of genera, requires the death of the animal and its careful preservation. The killing of mussels for identification is strongly discouraged, as it is rarely required in our area to make an accurate determination. In addition, many of our species are legally protected by state and federal law. Careful observation, notetaking, photography, and examination of spent shells are recommended instead. For information on regulations governing the collection of mussel specimens or spent shells, please go to: Permits
Introductory figures pointing out mussel parts for analyses.
Mussel features: Anterior and Posterior
Among the external features most useful for identification, the types of shell shapes are described by their resemblance to geometric figures.
Appearing as concentric circles of ridges or contrasting bands of color that mark the stages of growth, growth lines vary among species.
The hinge "teeth" are small structures of irregular shape and size that hold the two halves of the shell together.
Specimen length and width are measured with the specimen held on edge.
The posterior end of the shell may have useful features for identification, including a pronounced posterior ridge in some species, often combined with a clearly defined posterior slope.
The arrangement and width of the rays is a diagnostic character for several species in our area.
Beak size, prominence and structure vary among species and may aid in identification.