Analysis of Collections | Mollusca Types in Great Britain

Analysis of Collections (March 2018)

Updated verison available here

By far the largest concentration of Mollusca types in the UK is in the Natural History Museum, London. But this is not the whole story. Most of the UK’s 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.

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 seven museums and c. 550 types considered. The addition of data from other museums, or on other taxa, could lead to further insights in future.

Molluscs from all major seas worldwide are represented, as are non-marine taxa from countries worldwide (Fig. 1). Europe (mainly Britain), Africa and Australasia are relatively better-covered than Asia or 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 case, each species was brand new to both the collector and his or her contemporaries.

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 UK 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. Such diverse circumstances add to the story of Britain’s museums, 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 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 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.

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

The majority of the scientific names that these types represent remain in use today (which is by no means always the case; see synonymy). Our estimate of the degree of synonymy, using MolluscaBase and other sources for current nomenclature, suggests that on average 70% of each author’s names are still accepted (Fig. 4), although of course most have moved genus. The high synonymy rate for Montagu - pioneer as he was - might relate to most species in the British fauna being widespread, and thus already described by other Europeans. The still higher rate for Marrat might reflect his being one of few British workers to flirt with the notorious methods of Bourguignat’s “Nouvelle Ecole”. Yet his types at Liverpool remain in demand by specialists. The low synonymy rate of other authors may in some cases be attributable to a lack of recent revisions. It is only thanks to the care that the collectors, and succeeding generations of curators, took of these collections that such material will be available for study in future.

Fig. 4. Number of taxa described, and number of authors, for each period.