This genus derives its common name from a fancied resemblance to a
miniature triumphal car.
Shell very thin, transparent, symmetrical, convex below, flat above,
valves unequal, form tricuspidated, cleft at the sides, open like a
cleft anteriorly, and tridentated posteriorly; summit truncated.
Hyalæa tridentata.
Hyalæa cuspidata.
_H. tridentata._ The three-toothed Hyalæa.
Transparent, horn-coloured, globular; tridentated posteriorly; summit
and two posterior sides open; finely striated transversely.