Analysis of Collections | Mollusca Types in Britain & Ireland

Analysis of Collections

By far the largest concentration of Mollusca types in Britain & Ireland is in the Natural History Museum, London. But this is not the whole story. Most of the larger cities, ports, and towns have (or had) public museums incorporating natural history collections. Often, these collections were part of the nucleus around which the museum was built or developed, particularly in the 19th century. There are individual details about each Museum’s collection here.

Thanks to previous workers, we knew when embarking upon this project where most of the larger Mollusca type holdings were. We encountered some surprises but also found that bringing the list of types together for the first time allows a little analysis. This is not of course a scientific dataset, but still shows some patterns across the museums and types considered. The charts now work dynamically to reflect the ongoing addition of data since March 2018 (for the earlier analysis, click here).

Molluscs from all major seas are represented, as are non-marine taxa from countries worldwide (Fig. 1). Former territories of the British Empire are especially well-represented (the total for Portugal is skewed by endemic land-snails described from Madeira). The Old World and Australasia are relatively better covered than the Americas. Most of the major taxonomic groups are represented, with a preponderance of Neogastropoda (including cones, murexes, whelks and olives) and the stylommatophoran land-snails. These are popular groups in any global shell collection - the difference being that in this particular case, every species was brand new to both the collector and his or her contemporaries. The addition of new museums to the database has substantially increased the representation of Cephalopoda (octopus and squid) and the other smaller molluscan groups.

Fig. 1. Countries/territories from which types came.

Notably, even some of the larger collections are dominated by the types of one or a few authors. Graphs of the proportion of types in each museum and the proportions described by the most prolific authors are remarkably similar (Fig. 2). This may reflect the non-random nature of deposition, where donors/sellers, and the curators/buyers, helped ensure each museum developed a good collection. However, this was seldom straightforward, and collections such as Hanley’s at Leeds, and Montagu’s at Exeter, had already been partially dispersed. Other authors were museum employees (Marrat at Liverpool, and Standen at Manchester) and so deposited locally, while Alder and Hancock were naturalists whose ties to their local museum at Newcastle were forged over decades. The types of Melvill, an Establishment figure who was both wealthy and generous, came to rest in at least four UK museums. The Linnean Society collection is of course unique in representing the works of Linnaeus. Such diverse circumstances add to the story of museums in Britain & Ireland, and emphasise the fact that no two of their natural history collections are equivalent.

Fig. 2. Proportions of the types in each museum, and those described by the most prolific authors.

Most of the types were collected and named, perhaps unsurprisingly, in the mid and late Victorian era (Fig. 3), in the middle of what Dance termed the “abundant years” of conchology. Exotica imported from across the British Empire dominate, although new taxa in and around Britain & Ireland were still being recognised. This was after all the period at which Melvill, who was to describe over a thousand species of mollusc, was at the peak of his output, and a whole new natural history museum, dedicated to the brothers Hancock, was opened in Newcastle. The major exception is Montagu’s much earlier Testacea Britannica… (1803), whose surviving types are nearly all in Exeter. The graph also shows how few molluscs discovered in the last 100 years are represented by types at the museums dealt with here. The collections at Cardiff are unusual in including much more material from this period. Many of the types in the smaller collections date from this period, when the number of authors involved was at is highest.

Fig. 3. Number of taxa described, and the number of authors, for each period.

Since this project began in 2016, MolluscaBase and other online taxonomic sources for Mollusca have improved immensely. By our estimates, over 50% of the types in the database bear names that are still used for species today. The rest of the names are synonyms, applying to species for which a pre-existing name is now given priority. The rate of synonymy varies considerably with each author. Revisionary work on under-studied fauna and families will need to take account of type specimens like those in this database. It is only thanks to the care that the collectors, and succeeding generations of curators, have taken of these collections that such material will be available for study in future.

Fig. 4. The 15 most prolific authors and their respective degree of synonymy for taxa they described.