This genus is very remarkable for having the pit or cavity divided into
two parts, the one at the end of the other; the ligament is partially
seen from the outside.
Ungulina oblonga.
Ungulina transversa.
_U. transversa._ The transverse Ungulina.
Shell vertical or longitudinal, rather irregular, not gaping, equivalve,
inequilateral, with summits little marked and decorticated; hinge
dorsal, formed by one short, primary cleft tooth, before an oblong pit,
divided by a small ligament, in which is inserted a sub-interior
ligament; colour yellowish brown.