Unio. MOLLUSCA. UNIONID^. 417 
marked by lines of growth ; hinge strong. — Sower. Min. Conch, t. clxxxv. — ■ 
In Crag. 
8. U. Solandrii — Transversely oblong-ovate, slightly arched, rather com- 
pressed, thin ; both extremities obtuse ; beaks small, rugose, hinge slender. 
— (Mya Pictorum, Brander., Foss. 105.) Sower. Min. Conch, t. Dxvii.~-In 
Crag. 
9. U. conciwmts.— Transversely oblong, ovate, depressed, nearly smooth, 
thick ; posterior side very small ; beaks prominent, recurved — Sower. Min. 
Conch, t. ccxxiii. — Tnfe^'ior Oolite. 
10. U. Urii — Transversely oblong, dorsal margin nearly straight ; une- 
qually striated by the lines of growth. — Muscle, Ure., Hist. Ruth. 311. 
t. xvi. f. 4. — Mya ovalis, Mart. Derb. t. xxvii. f. 1, 2. — In Slate Clay of the 
Coal Formation. 
Gen. CVIIT. ALASMODON. — -Shell transverse, hinge with 
a single tooth in the right valve, recurved into a divided 
tooth in the left ; no lateral teeth. 
429. A. margarityirum. — Ventral margin slightly concave ; 
shell, towards the ligamental margin, compressed. 
Musculus niger. List. Conch, t. cxlix — Mya margaritifera, Linn. Syst* 
i. 1112. Mont. Test. Brit. 33. — ^Unio marg. Turt. Biv. Brit. 249« 
t. xvi. f. 1. — In gravel in rapid streams. 
Length about 2, breadth upwards of 4 inches j cuticle brownish black j 
beaks worn, shell thick ; the lines of growth fine ; inside pearly. Pearls are 
frequently met with in this species. 
CARDITAD^. 
Gen. CARDITA. — Shell inequilateral ; hinge with two teeth, 
the shortest beneath the beaks, the other oblique and mar- 
ginal beneath the insertion of the cartilage. 
1. C. striata — Quadrangular, gibbous ; the beaks placed at one of the an.< 
gles ; obliquely striated from the beaks to the edge Sower. Min. Conch. 
t. Ixxxix. f. \. —Inferior Oolite. 
2. C. abrupta — Triangular gibbous, beaks projecting near one angle ; ob- 
liquely striated ; anterior side longitudinally striated ; five or six transverse 
reflected ridges along the front — Sower. Min. Conch, t Ixxxix. f. 2.~-Inferior 
Oolite. 
3. C. tuherculata. — Heart-shaped, longitudinally radiated, radii tuberculat- 
ed ; valves equal, laterally compressed, longitudinally subcarinate, one side 
semilobate, the other nearly flat, beaks much incurved. — Sower. Min. Conch, 
t. cxliii. In Green Sand. 
4. C. lunulata — Rhomboidal, pointed, gibbose, transversely costated an- 
terior part separated by a projecting serrated keel, lunette deeply excavated ; 
beaks involute. Sower. Min. Conch, t. ccxxxii. f. 1, 2. Inferior Oolite. 
VOL. I. Dd 
