444 
CONCHIFERA. 
Unio piclorum. —The Painter’s Unio. 
Plate LXXX1X. fig. 3. 
Oblong-ovate, strong, anterior side rhomboid and attenuated ; 
the opposite side obtusely acute; the umbones, somewhat 
warted; with a dusky-green epidermis, and concentrically 
wrinkled. Nearly three inches broad. Inhabits the rivers of 
Europe. 
TRIBE II.-TRIGONACEA. 
With a primary lamelliform, and transversely striated tooth. 
Inhabits the Ocean. 
Genus 8. — CAST ALIA.— Lamarck. 
Generic Character. —Equivalve, inequilateral, trigonal; the 
umbones decorticated, and inflected before; hinge with two 
lamellary teeth, transversely striated, one posterior, remote, ab¬ 
breviated and subtrilamellar tooth ; another elongated and lat¬ 
eral ; ligament external. 
Castalia ambigua — The Ambiguous Castalia. 
Plate LXXXIX. fig. 4. 
Ovate, oblique, the umbones truncated ; longitudinally ribbed, 
with distant transverse striae; epidermis pale chestnut brown ; 
inside pearly. Habitat unknown. 
Genus 9—TRIGONIA.— Lamarck. 
Generic Character. —Equivalve, inequilateral, trigonal, and 
sometimes orbicular; teeth of the hinge oblong, laterally com¬ 
pressed, diverging, with transverse furrows; two in the right 
valve, grooved on both sides ; and four in the left valve grooved 
on one side ; ligament marginal and external. 
Trigonia peciinata _ The Toothed Tiugonia. 
Plate LXXXIX. fig. 5. 
Suborbicular, with radiated or divergent, prominent, and 
somewhat scaly ribs ; inside pearly ; margin crenulated. One 
inch and three-fourths broad. Inhabits the Australian seas. 
TRIBE III.-ARCACEA. 
Primary teeth small, numerous, and disposed in a line in 
