Griffin & Nielsen (2008):
TYPE MATERIAL. Two syntypes: NHM-L27968 and NHM-L27969 (Santa Cruz).
REMARKS. Sowerby’s figure is probably a composite of the two syntypes, showing the size and shape of the smaller and reasonably complete articulated internal mould NHM-L27968, and the faint sculptural remnant of the other, larger and incomplete mould of one valve MBNH-L27969, which is about one and a half times the size of the smaller specimen. Rib pattern suggests that this species fits better in Hedecardium Marwick, 1924 [type species Cardium waitakiensis Suter, 1907], than in Trachycardium Mörch, 1853 [type species Cardium isocardia Linnaeus, 1758], where it was placed by Frassinetti & Covacevich (1999).
Descriptions of Tertiary fossil shells from South America..
In: Geological observations on South America. Eds: Darwin, C.. p. 249-264
Tertiary invertebrates: Reports of the Princeton Expedition to Patagonia, 1896–1899. Vol. 4(2) p. 45-332
Frassinetti,D.. and Covacevich,V.. (1999):
Invertebrados fosiles marinos de la Formacion Guadal (Oligoceno superior-Mioceneo inferior) en Pampa Castillo, region de Aisen, Chile Translated Title: Invertebrate marine fossils from the Guadal Formation (upper Oligocene-lower Miocene) at Pampa Castillo, Aisen region, Chile.. Vol. 51 p. 96
Griffin,M.. and Nielsen,S.N.. (2008):
A revision of the type specimens of Tertiary molluscs from Chile and Argentina described by d’Orbigny (1842), Sowerby (1846), and Hupé (1854) . Journal of Systematic Palaeontology