The study of biodiversity is often hindered by the existence of complexes of morphologically similar species. However, most of the times, the so-called cryptic species are, indeed, distinguishable if the adequate characters are compared. There are 6 accepted species of the genus Limacia Müller, 1781 in the world, but only one of them, Limacia clavigera (O. F. Müller, 1776), is known in Europe. In September 2010, during the course of a regular biodiversity survey in the north east coast of Spain, a small polycerid was captured and misidentified with L. clavigera. This animal is described as a new species in this paper, and discussed with L. clavigera and with its other Atlantic congener, Limacia annulata Vallès, Valdés & Ortea, 2000. In addition, the taxonomic history of Limacia is summarized, the rest of the species of the genus are compared, some potentially controversial cases are analysed and new data are given on the morphology of the spicules of the types of L. annulata.