Lyonsiella Friele 1879

Lyonsiella Friele, 1879 Type species: Lyonsiella abyssicola M Sars, 1868, nomen nudum. Pecchiolia abyssicola GO Sars, 1872 by subsequent designation of Soot-Ryen (1966). Description Shell: Oval to subquadrate, thin, fragile, inflated, inequivalve; right valve slightly larger than less. Inequilateral, anteroposterior axis inclined in relationship to the dorsoventral axis. Surface covered by radial lines, striae, minute spines, or pustules. Presence of a weak lunule in the anterodorsal margin. Hinge toothless. Internal ligament located in a longitudinal groove on the posterodorsal margin and associated with a well-developed and elongated lithodesma. Soft parts: Gill moderately reduced. Exhalant siphon short, conical, and somewhat prominent. Inhalant siphon large and eversible, with an inner ring of arborescent tentacles on the edge of the aperture covered by small papillae. Both siphons are surrounded by an outer ring of small conical tentacles. Remarks M. Sars (1868) used the name Lyonsiella abyssicola for specimens collected in deep waters near the Lofoten Islands (Norway), thus establishing a new species and genus name. However, he did not provide any description for either, thereby failing to comply with the requirements of Article 12 of the ICZN, rendering this name a nomen nudum in both instances. Many authors (Poutiers and Bernard 1995, Oliveira and Absalão 2010a, Coan and Valentich Scott 2012) attribute the genus to G. O. Sars (1872), because he redescribed the species Lyonsiella abyssicola accordingly. However, G. O. Sars (1872) placed it within Pecchiolia Savi & Meneghini, 1850, not Lyonsiella. In concordance with Soot-Ryen (1966), Friele (1879) was the first to assign the valid species Pecchiolia abyssciola to the genus Lyonsiella. Consequently, Lyonsiella should be attributed to Friele (1879) and not to G. O. Sars (1872).