Cardiomya sp. 1 Fig. 6 A–B Cardiomya cleryana auct., non d’Orbigny, 1842 – Barroso et al. 2016: in part. Material examined BRAZIL – Amapá state • [1v]; northwest of Amazon Canyons; 03°37′00″ S, 50°01′00″ W; 72 m depth; 08 May 1971; GEOMAR III, stn 193; CMPHRM 3681. Description Shell small (length 7.8 mm; height 6.1 mm). Shell flank elliptical, umbones blunt. Anterodorsal margin forming a shoulder, anterior margin truncated, ventral margin rounded, crenulated. Rostrum very short, truncated, posteroventral sinuation shallow, posterodorsal margin curved upwards, extending a little above the umbones. External sculpture of 22 radial ribs, less spaced towards the anterior region, the four strongest and most widely spaced ribs at the posterior end of the shell flank; rostrum with four radial lines. Geographic distribution Brazil, Amapá state, northwest of Amazon Canyons, 72 m. Remarks Part of the specimens listed as Cardiomya cleryana in Barroso et al. (2016: 6) (CMPHRM 3681) are here reassigned to Cardiomya sp. 1. Cardiomya surinamensis van Regteren Altena, 1971 is similar to Cardiomya sp. 1, but can be distinguished from it by its weak radial ribs, which vanish towards the anterior region, and the wide rostrum, devoid of radial ornamentation.

Published as part of Lima, Tarcilla Carvalho De, Oliveira, Cléo Dilnei de Castro & Absalão, Ricardo Silva, 2020, Small, rare and little known: new records and species of Cardiomya (Bivalvia: Cuspidariidae) from Brazil, pp. 1-20 in European Journal of Taxonomy 619 on page 13, DOI: 10.5852/ejt.2020.619, http://zenodo.org/record/3777241