A Post from the Past 
Sharp underfoot but not on the chin, the razor shells take their name from their similar shape to the old cut-throat razors.
Razor shell molluscs are nifty beasts. These bivalves have long narrow hinged valves or shells. They can bury deep down into the sediments and are able to move up and down with great rapidity using a long muscular foot that looks like a pale extensible tongue. They maintain contact with the surface water by means of two short fused tubes or siphons through which they suck in waterborne food particles and exhale waste products.
If you are lucky enough to see a living razor shell at the surface, you will need to be even luckier to catch one. They can sense the vibration of your approaching footstep and will shoot downwards at top speed before you can reach them.
There are several types of razor shells in Rhossili Bay where they occur in greatest abundance especially in the more sheltered southern corner of the beach by Worms Head. On this particular February visit, most of the empty razor shells on the strandline were the pod-shaped Pharus legumen (Linnaeus) illustrated below. Actually, these are not “true” razor shells but share many of the same general features and life habits. They are mainly distinguished by the ligament joining the two halves of the shell being located midway along the length of the shell rather than right towards the end of the long side as in true razors. This species is not mentioned as being typical of Rhossili beach in Jonathan Mullard’s Collins New Naturalist book on Gower.
I also found a few of the larger pod razor shells, Ensis siliqua (Linnaeus) – an example is shown in the photograph above. Both types of razor are very brittle and fragile – getting easily crushed underfoot into small sharp pieces. In previous summers I have seen hundreds of thousands of empty razor shells, of even more species than mentioned here, washed up on the shore close to the bottom of the steps that take visitors from Rhossili village down to the beach.
© Jessica Winder and Jessica’s Nature Blog, 2009