Mulinia bicolor Gray, 1837

(Figure 5)

Mulinia bicolor Gray, 1837: 375; Hanley, 1843: 34, pl. 10, fig. 31; Dall, 1909: 274; Bernard, 1983: 40.

Mactra bicolor Gray, 1837 . d’Orbigny, 1846: 510, pl. 78 fig. 18; Hupé in Gay, 1854: 348, Philippi, 1893: 11, pl. 3, fig. 9.

Diagnosis. Shell subcircular, large, inflated; posterior area not defined by line or keel; umbos inflated.

Description. Shell trigonal, subcircular; maximum length up to 12, 25 cm; anterior and posterior ends rounded; ventral margin curved. External surface smooth, with yellow to brownish periostracum (Fig. 5 A–B). Right hinge with two anterior (AI & AIII) and two posterior (PI & PIII) lateral teeth; anterior teeth similar in length, dorsal tooth stronger than ventral one; ventral posterior lateral tooth more elongated than dorsal; two unfused cardinal teeth (3a & 3b) flanked by accessory lamella (Fig. 5 C); left valve with one elongated anterior lateral teeth (AII); posterior lateral tooth (PII) shorter; cardinals fused, V-shaped (Fig. 5 D).

Type material. Holotype (NHM 196323), one left valve.

Type locality. Unknown, not indicated in the original description.

Other material examined. Chile. South America (NHM 1843.661, 2; 68.7.6.22, 1 1962.1090, 3); Chile (AMNH 34042, 2); Talcahuano, Chile (MACN 13804, 8 valves with periostracum).

Distribution. Caldera to Talcahuano, Chile.

Remarks. The distribution of this species was mentioned by Soot-Ryen (1959) and Osorio et al. (1979), and later confirmed by González et al. (2002). Mulinia bicolor is a Recent valid species present on the south-central coast of Chile. This is one of the largest species of the genus (holotype length: 12.25 cm). Despite its large size, it is a very rare species judged by its presence in the collections studied (only eight specimens were analyzed) M. bicolor was included by Gray (1837) in a group of taxa with the anterior end delimited by a line. The type material housed at NHM agrees with d´Orbigny’s (1846) description. In addition, the French author pointed out the larger size of this form compared with the type material of Mulinia edulis and M. byronensis . The illustrations labeled as M. bicolor published by Hanley (1843: 34, pl. 10, fig. 31) and Philippi (1893: 11, pl. 3, fig. 9) are not adequate to confirm the taxonomic status of Gray species.