Diagnostic characters
Shell helicoid with moderately high spire; whorls tumid and sutures distinct; outer lip meets last whorl at right angles. Umbilicus large, usually rounded. One subsutural row of brown marks on last whorl. Animal as in E. nitida.

Other characters
The shell of this animal is in most respects like that of E. nitida apart from the points mentioned above. Although the umbilicus is usually rounded at its adapical end it may be pointed as in E. nitida; the ridge which in that species runs into the umbilicus from the middle of the columella is here reduced or absent. The colour of the shell is less intense than in E. nitida with the umbilical groove pale. Up to 30 mm high, 30 mm broad; last whorl occupies about 90% of shell height, aperture about 70%. The animal is like E. nitida.
E. catena has the same way of life as E. nitida but is restricted to shallower water, from L.W.S.T. to 125 m deep. Its distribution in the British Isles and abroad is also similar, but it is absent from Scandinavia.
Breeding occurs throughout spring and early summer when egg collars may be found washed up on sandy beaches. They may be distinguished from those of E. nitida first by their size, the diameter of the collar being about 75 mm, and second by the arrangement of the egg capsules within the collar: these lie in regular lines and bulge a little on its external surfaces. Each capsule contains many eggs (80-90) but of these only two or so develop to veliger larvae, the rest being used by them as food.