Type material examined. The specimen illustrated by Chemnitz (1782; figs 371, 372; Nicobar Island, Spengler collection ZMUC), used as the basis for Roding's (1798) description of L. polita, has been isolated and is here figured and designated as the lectotype in order to fix the type. Dimensions of lectotype: length 41.5 mm, height 35 mm, width of paired valves 27 mm.
Other material examined. Specimen from MNHN, marked on associated label 'Cytherea sutcatina Lamarck var 2. Individual named by Lamarck. No status'.
Diagnosis
Shell solid, trigonal, smooth to glossy, moderately inflated, posteriorly attenuated; umbones strongly prosogyrate; lunule heart-shaped, flat, delineated by well-incised line. Sculpture of flattened concentric ridges posteriorly and growth pauses. Colour externally white with dark, radial, brown or orange rays, often interacting with rays composed of zigzag or chevron patterns; umbones white or light brown, lunule brownish; shell internally white, sometimes brown or orange medially. Shell length to 41.5 mm.
Distribution and habitat Northern Indian Ocean, littoral areas, in sandy mud.
Lioconcha polita can best be compared with L. sowerbyi, but the strong groove surrounding the lunule, greater inflation, broad radial colour bands and internally orange or light brown centrally (weak lunule groove, moderate inflation, thin zigzag patterns and deep brown internal colour in L. sowerbyi) distinguish the two species. Compared with L. annettae, which is also attenuated posteriorly, the broad external radial colour bands, internal orange or light brown colour (sparse tent patterns and yellow internal colour in L. annettae) separate the species. The lectotype of L. polita is an interesting specimen in that the right and left valves show marked differences in colour patterns, this caused some authors (Lamprell and Whitehead 1992; Lamprell and Stanisic 1996; Lamprell and Kilburn 1999a, 1999/>) to deal with the two Chemnitz (1782) figures (371 and 372) as two separate species. Examination of the specimen from the ZMUC and the Lamarck specimen from the MNHN also show this colour variation; however, the specimen MHNG. 1084-24 marked ''Cytherea sulcatina Lamarck, 1818 holotype' does not.