This genus has several characteristics which distinguish it from the
Ostrea; they are free; the valves and the apices are nearly equal, with
a projecting callosity on each valve, depressed underneath, and
obliquely arched for the reception of the ligament.
Shell sub-nacreous, sub-regular, sub-equivalve, inequilateral; upper
valve finely granulated, or striated longitudinally from the apex to the
margin; summits anterior, distant, recurved below; hinge without teeth;
ligament undivided, thick, inserted in a rounded cavity, made in a
slightly projecting callosity on each valve; muscular impression
sub-central, rather large, and two very small ones entirely anterior.
_V. lingulata._ The tongue-like Vulsella. Pl. 15, fig. 6.
Elongated, depressed, transversely striated; pale yellowish brown, with
longitudinal darker stripes.