In some individuals, small spines or scales are found on the posterior ends (furthest from the hinge) of the larger ribs.

[2][5] Carditamera affinis is found in the eastern Pacific Ocean from California to Peru.

[6] It is also found in the Gulf of California and was one of the specimens collected there by John Steinbeck and Ed Ricketts, as recounted in The Log From The Sea Of Cortez.

[7] This is a shallow-water species, living from the intertidal zone down to 27 meters (90 feet) deep.

[4] Carditamera affinis is a filter feeder, straining nutrients from sea water that it pumps through its body.