A large anemone (base up to 15 cm diameter) with up to 160 short (up to 2 cm), stout tentacles arranged in multiples of ten. Individuals from offshore tend to be larger. The coloration is very variable, ranging through white, yellow, orange, red, blue, grey, purple and brown being either plain or more commonly in some combination. Perhaps most commonly with a red column blotched with green/grey and a prominent pattern of red lines amongst the tentacle bases. The tentacles are usually banded but may be plain. There are numerous grey warts on the column to which gravel and shell fragments stick. When the tentacles are fully retracted, the body of the anemones may be almost obscured by these adherent particles.The taxonomy and relationships of this sea anemone are in some confusion with anemones of very similar appearance and apparently reproductive biology to Urticina felina occurring on the north-west (Pacific) coast of north America. An attempt is made below to establish relationships important for using literature to support sensitivity and recoverability assessments elsewhere in this review. Stephenson (1935) identifies "Tealia (=Urticina) crassicornis" of Müller as a variety (crassicornis) of Tealia (=Urticina) felina (L.) but not the variety coriacea which is the "Tealia crassicornis" of Gosse (1860). However, Stephenson notes that, in his "var. crassicornis", the embryos develop up to a late stage in the coelenteron of the parent and later describes it as "viviparity". Since Appelöff (1900) cited in Chia & Spaulding (1972) reported that, in Europe, Tealia (=Urticina) crassicornis releases it's gametes freely into the sea (i.e. is not viviparous) and that the species they studied in the northwest USA similarly produced ova and sperm, it seems likely that their "Tealia crassicornis" has closer affinities to the British "Urticina felina" than to the species that occurs further north of the British Isles and is called "Tealia crassicornis (Müller)".