Simnia patula: -50m, Trawled, Devon, Southwest England, United Kingdom, 25.4mm.
The « Poached Egg Shell » is a beautiful and frail ovulid ranging from Norway to Canary Islands, and into the Mediterranean Sea. A carnivore and ectoparasite of octocorals and hydroids, it lives in moderately deep sublittoral water around -20-120m. Its most common hosts are the soft coral Alcyonium digitatum L, 1758 (« Dead Man's Fingers »), the sea fan Eunicella verrucosa (Pallas, 1766), and the hydroid Tubularia indivisa L, 1758. The shell is variable in colouration from white to cream to dark orange as well as shape of the extremities, while the mantle is decorated with brown streaks and spots. Although a comm.on species in its natural environment, it is an uncomm.on to rather rare species on the shell trade especially in good condition. Typical shell length around 20mm., very large specimens like the one shown may exceed 25mm. Its type locality is Weymouth, Dorset, England.

Simnia patula: Diagnostic characters
Shell thin, glossy, convolute; aperture narrow, with lips longer than other parts of the shell. Shell covered by mantle in active animals. Dorsal surface of anterior part of foot ridged longitudinally; operculum absent.
Other characters
No spire is visible in fully grown shells. The slight ornament includes growth lines and low spiral ridges, the latter more easily seen at the extremities of the shell. The elongated aperture is drawn out at each end to a canal, the basal inhalant one broader and less distinct from the aperture than the apical exhalant one. White, yellowish, or pinkish. Up to 15 mm high, 7-8mm broad. In young shells the spire of three tumid whorls is still exposed.
The head has a short snout ending in a suctorial disk with central mouth. Cephalic tentacles are long and have each a basal eye. The mantle edge forms an inhalant siphon anteriorly, and, laterally, two flaps which may cover the shell. Males have a long, recurved and pointed penis carrying an open seminal groove. The foot is rather large. The body is yellow with brown streaks and spots, mostly on the exposed mantle lobes; the distal half of each tentacle is white, its tip brown; front end of the foot pinkish.
S. patula is not common around the British Isles, confined to the western Channel and western coasts north to Orkney (Rendall, 1936). It is not intertidal, living 15-75 m deep on colonies of Eunicella, Alcyonium and Tubularia on which it feeds (Fretter, 1951a). Its further range is south to Spain.
Eggs are laid in capsules spread in a layer over Alcyonium colonies. They produce veliger larvae which ultimately possess a velum of four long and very narrow lobes (Lebour, 1932a).