Easily distinguished from the Unio by a compound cardinal tooth, which
slopes in an inclined position towards the posterior side. They are more
found in lakes than in rivers.
Shell solid, pearly, equivalve, obliquely triangular, auriculated; base
truncated and straight; hinge with two projecting teeth; the cardinal
divided into numerous divergent parts; anterior ones smaller, the others
long and lamellar.
Hyria avicularis.
Hyria corrugata.
_H. avicularis._ The little bird Hyria. Pl. 5, fig. 4.
Umbones smooth and polished; ears large, with pointed terminations;
finely striated; interior pearly, exterior of a rich reddish
golden-yellow colour; covered with a greenish brown epidermis.