Unto. MOLLUSCA. UNIONID^. 417 



marked by lines of growth ; hinge strong. — Sower. Min. Conch, t. clxxxv. — 

 In Crap. 



0. U. Solandrri 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 

 Craff. 



9. U. concinnus Transversely oblong, ovate, depressed, nearly smooth, 



thick ; posterior side very small ; beaks prominent, recurved — Soiver. Min. 

 Conch, t. ccxxiii. — Inferior Oolite. 



10. U. Uni — Transversely oblong, dorsal margin nearly straight ; une- 

 qually striated by tke 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. CVIII. ALASMODON.— Shell transverse, hinge with 

 a single tootli in the right valve, recurved into a divided 

 tooth in the left ; no lateral teeth. 



429. A. margaritifbrum. — Ventral margin slightly concave ; 



shell, towards the ligamcntal margin, compressed. 



Musculus niger. List. Conch, t. cxlix Mva margaritifera, Linn. Syst* 



i. 1112. Mont. Test. Brit. 33 — Unio marg. Tiirt. Biv. Brit. 249- 

 t. xvi. f. 1 In gravel in rapid streams. 



I^ength about 2, breadth upwards of 4 inches ; cuticle brownish black ; 

 beaks worn, shell thick ; the lines of growth fine ; inside pearly. Pearls are 

 frequently met with in this species. 



CARDITADiE. 



Gen. CARDITA. — Shell inequilateral ; hinge with two teeth, 

 the shortest beneath the heaks, 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. 1 — 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. tuberculata — 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^ 

 tenor part separated by a projecting serrated keel, lunette deeply excavated ; 

 beaks involute. Sower. Min. Conch, t. ccxxxii. f. 1, 2. Inferior Oolite. 



VOL. I. B d 



