Mactra, the right valve of the Rangia; brackish water, Florida.
Mactra; British (figs.
In some Lamellibranchs (Pecten, Spondylus, Pholas, Mactra, Tellina, Pectunculus, Galeomma, &c.), although cephalic eyes are generally absent, special eyes are developed on the free margin of the mantle-skirt, apparently by the modification of tentacles commonly found there.
Such eyes on the mantle-edge are found in Pecten, Spondylus, Lima, Pinna, Pectunculus, Modiola, Cardium, Tellina, Mactra, Venus, Solen, Pholas and Galeomma.
The embryo is provided with ten hooks, and appears to select Lamellibranchs (Mactra) for its intermediate host.