Shell oval to circular, fan-like, ear-like, disc-like (narrow at the umbo) and umbo at the center. Hinge typically with wing-like expansions and without teeth. Both valve flattish, and either top valve flattish or bottom valve slightly convex, sculpture differs on opposite valves. Hinge ligament internal, single adductor muscle and pallial sinus absent. Many species are capable of swimming by clapping their valve. Most species are tropical, but a few live in polar water.
Genus: Ylistrum Mynhardt & Alejandrino, 2014
Species: Ylistrum balloti Bernardi, 1861
Moderate size and shell height up to 110 mm. External color of top valve is reddish, covered with concentric pattern from umbo to ventral margin of many thin brown lines and violet-brown spots, light brown or pale reddish stripes transverse valve height; auricles often similar in color to base color of left valve. External bottom valve white, with concentric, irregularly sized violet-brown spots; valve interior white, becoming a brown or yellow tint along the margins of one or both valve; interior ribbing on both valves, 32-39 on top valve, 37-47 on bottom valve.
Pecten balloti Bernardi, 1861; Amusium balloti Iredale, 1939; Dijkstra, 1988. Amusium japonicum balloti Habe, 1964.
Ylistrum balloti Bernardi, 1861- [Mynhardt et al. (2014): 407]
Tropical and subtropical Indo-Pacific Ocean
This taxon has not yet been assessed for the IUCN Red List