CONCHIFERA. 
443 
Genu ft 5. — ANODONTA. — Lamarck. 
Generic Character. — Equivalve, inequilateral and transverse; 
hinge linear, without teeth ; a glabrous plate, lamina smooth, 
truncated or forming a sinus at the anterior end, terminating 
the apex of the shell; two lateral, remote, twin, muscular, im¬ 
pressions ; ligament linear, external, sunk in a cleft at the an¬ 
terior extremity. 
Anodunta cygnea. — The Swan Anodonta. 
Plate LXXXIX. fig. I. 
Ovate, thin, convex, somewhat compressed on the anterior 
side; with concentric wrinkles; covered with a green epider¬ 
mis, frequently brown towards the umbo ; inside pearly white ; 
beak small and ventricose. Three inches long, and seven broad. 
Inhabits fresh water lakes in Europe. 
Genus 6.—HYRJA. — Lamarck. 
Generic Character —Equivalve, oblique, trigonal, eared, with 
the apex truncated and parallel, hinge with spreading teeth, 
the posterior one cleft into numerous divergent portions; the 
lateral or anterior tooth strong, elongated and lamellar; ligament 
linear, and exterior. 
Hyria avicularis. — The Little-Bird Hyria. 
Plate LXXXIX. fig. 2. 
Umbones smooth and produced; ears large, with pointed 
terminations; a greenish-brown epidermis, and finely striated ; 
inside pearly, and of a rich reddish golden-yellow. Three 
inches broad. Inhabits the rivers of America. 
Genus 7.— UNIO.— Lamarck. 
Generic Character.— Shell transverse, equivalve, inequilateral, 
free; umbones decorticated, and somewhat worn; posterior 
muscular impression compound ; hinge with two teeth in each 
valve ; the cardinal tooth short, irregular, cleft, and striated; 
the other oblong, laterally compressed, and produced when aged ; 
ligament external. 
Section * With a short, thick, primary tooth. ** Primary 
tooth short, compressed, and frequently crested. 
