Snail trouble (and a database of photos)

The two snails I identified yesterday were easy to key out. But the one I picked up next was small. So is it a juvenile snail? Or is it an adult of a small species? If it's a juvenile its measurements won't fit the ones in the keys, so I'll immediately be barking up the wrong tree.

What we ideally need is someone who knows. This is a good tip for any type of creature or plant you're interested in. Sadly I don't know anyone and Mr Adams is long dead. I could join a local group of snail fanatics or take a course. But in the meantime I have sought some information from books and the internet...

Cameron says that adults of many species have a lip (or teeth) to their shell. But sadly many do not, so that's not altogether helpful.

However, the British Conchological Society key says on this page that if the maximum shell breadth is less than 8mm and the number of whorls is less than 3 and a half, you probably have a juvenile (with the implication it's worth looking for another specimen if you actually want to have a chance of identifying anything). But if your snail has 4 or more whorls, even if it's less than 8mm, then you probably have an adult.

You count the whorls by running an imaginary line from the centre of the spiral, out so it forms a semi-circle with the first part. You count from the end of that semi-circle: each time you return to the line, it's a whorl. It can be difficult to tell where to start counting the whorls because they're so tiny in the centre (the 'protoconch').
 

 

Here's my little snail, it's just over 8mm wide. You can borrow some vernier callipers from me if you want to measure your snails - they are easier than using a ruler. You can see this one has about 4 whorls, so I'm going to assume it's an adult.

Here's its underside - you can see it's got an 'umbilicus' - a hole where the whorls don't totally close up on themselves.

This is not the world's best photo, but it's to try to show the flatness of the shell - this doesn't look like your average conical garden snail.

Using the pictoral key in Cameron's book, it's easy to pick out the right section - it's >7mm wide, and it's  flattened, glossy or waxy with no lip and no patterns or bands (it's quite shiny). This puts it in the 'Zonitidae',  or Glass Snails.

But now another problem - the key brings us to a pair of statements which seem very difficult to decide between. It even says, omniously, to 'take special care as the distinction can be hard to make'. But the accompanying drawings of rapidly vs. slowly expanding whorls look exactly the same to me.

This is no time to be loyal to one key, so I leapt to try Daw and Ivison's Bristol key - this brought me out at a similar dilemma - I'm left to choose between a number of Aegopinella, Oxychilus and Zonitoides species, all of which seemingly have similar characteristics with their flattened spires, colours, and sizes. It doesn't help that my specimen is empty and it would be useful to have information about its one-time occupant's body. Perhaps this shows there's something to be said for collecting live specimens.

I'm going to draw myself a little table and try to work this one out. Cameron soothingly says 'Do not expect to identify every shell you find.' But I'm going to persist for a while longer.

The tortuous workings of the mind of an extreme amateur snail identifier

After much agonising I have decided on Aegopinella nitidula, commonly known as the 'Smooth Glass Snail'. The size, number of whorls and 'opaque milky flush round the umbilicus' swung it. I might be wrong yet, through sheer lack of experience. I need to keep this one and compare it with similar-looking specimens in the future.

I've found lots of photos on AnimalBase,  which is run by a university in Germany, and the photos were contributed by European malacologists so you can be confident in their identification. Their search page is here.

Names have changed since Mr Adams' day, but it's comforting to hear him say that "this interesting genus often gives more trouble to the novice than all the rest of the British land and freshwater shells put together, except the vexatious Pisidia." Those vexatious little Pisidias eh. He also advises that "the animals should be studied and compared", meaning that their bodies differ in appearance, not just their shells.

And speaking of names and terminology, you may like Mr Adams' Snail Glossary as much as I do: it gives the English translation of Latin names like 'splendens' (shining) and 'punctata' (marked with minute spots) - but also of the names of parts of snails and shells which you may come across (eg umbo and operculum). Pisidium by the way means 'like a pea' - it's the group of tiny freshwater clams.