Our list doesn't contain this information. We have always aimed to stock the most varied range of shells possible, and this can mean stocking small quantities of each species – often we only obtain a single specimen. The size column can give you a clue: if only one size is given (eg 28mm) then quite likely there is only a single specimen; if a range is given (eg 28–30mm) or a plus sign (eg 28mm+) then there were multiple specimens available when they were originally listed. Usually, about half the items on the list are single specimens. There are relatively few species that we stock in quantities of 10 upwards.

We use an extensively modified HMS-ISGS system of quality grading, because we don't believe that system takes into account the demands of modern collectors. We use intermediate grades (eg F+/F++) because they add vital extra information on which to base your decision. In decreasing order of quality, our grades are: G- (Gem-), F+++, F++, F+/F++, F+, F/F+, F, Gd (good) and Fr (fair). We believe that very few shells are truly gem, and so we tend to avoid that description. In some families, specimens never come better than F++, and a lot of cold-water species never even reach that quality. It must be noted that shell grading is always going to be at least 90% subjective – the buyer really needs to get used to the gradings given by an individual dealer. We believe that we grade 'harsher' than most European dealers, and far harsher than dealers in developing countries.

It's simply supply and demand. Even with shells like Cypraea, only a small proportion of a population will be close to gem. Using the internet, modern collectors are able to pick shells from a wider range of sources than ever, and are increasingly demanding about quality; and yet the supply of top quality shells has remained the same. This means that there are huge differences in the prices of shells that might sound quite similar in quality. The quality grades you buy really are a matter of personal choice. Some collectors only buy F+++ specimens, and if they apply these descriptions rigorously they effectively limit themselves to a handful of families. Other collectors prefer to buy F+ and F++ specimens and make their money go much farther; and this expands the range of families they can collect.

The size is the maximum measurement that can be obtained in any direction – this is most often the apex-to-canal height for gastropods, but not always. This is the standard used by all shell dealers. For Spondylus our measurements include the spines, and for Xenophora they include the attachments.

A species might be common in one locality but rare in another. Advanced collectors want to obtain specimens from throughout the range of the species, and are willing to pay extra for the rare locality – even though the shells themselves may be indistinguishable. Also, the cost of human resources (eg divers, fishermen) varies significantly throughout the world, and this is usually reflected in the price of the shells.

The vast majority are obtained straight from source and are freshly collected. Typically they will appear on our list about two months after being collected. The colours of our shells tend to be much better than those from dealers who buy up old collections.

To get the variety we need we have to rely on a network of collectors around the world, plus two major collecting trips each year.

We use books and scientific papers, some excellent websites, our own image library, and, most importantly, our network of experts. No single source is ever going to be adequate for identifying shells.

Shell dealers try hard to identify shells correctly, but none can claim a 100% accuracy rate. When mistakes happen, as they inevitably do, this company either asks for the shell to be returned (and pays the costs), or suggests that the customer keep the shell but pays a lower price (if the species turns out to be more common than was thought). In most such cases though, the real ID is actually rarer than the one we gave, and the customer is more than happy to keep the shell.

You are very welcome to send us your list of what shells you want. We will inform you if they become available.

We love to sell the very aesthetic shells that appeal to everyone. However, certain shells are very heavy in relation to their value, and by the time we have obtained them from their source a significant proportion of the value will be due to the postage costs. Since the vast majority of our business is mail order, you the collector would then have to pay postage again. Most shells in this category are readily available for sale however, on the internet (eBay etc) or in shops. Please note that some large shells that are relatively common are either on the CITES list (eg Tridacna spp., Strombus gigas) or are subject to local collecting restrictions (eg Cassis cornuta). We never deal in these species.

Freak specimens are deformed in some way during their lifetime, either by a genetic defect or by environmental effects. Many collectors find these freaks particularly interesting, and they are always in demand.

Freshwater shells are growing in popularity, and we believe we offer one of the best selections in the world. There are separate galleries for freshwater gastropods and freshwater bivalves and they have their own sections at the end of the list.

We have a small selection of fossil species for sale, although we don't have regular sources of supply.

Sometimes we have unsorted micro shells from Philippine tangle nets. These are very popular with advanced collectors, as they offer real possibilities of discovering new species. Please let us know if you are interested in this sort of material, because it normally sells before we have chance to include it on the list.

No. Many corals are on the CITES list and collecting live corals inevitably damages reefs.