142 DIMYAIKA. 



one large dilated projecting and nearly vertical primary tooth in 

 the left valve, and with a hollow in the opposite valve ; ligament 

 internal, short, thick, and inserted in the hollow of the primary 

 tooth on the one side, and in the pit of the other valve. 



Mya truncata. — The TKVi^CATEn Mya. Plate XVIII. fig. 

 6. Suboval, truncated, and gaping greatly at the smaller end ; 

 much rounded at the other ; covered with a yellowish-brown 

 epidermis ; wrinkled transversely ; inside white. Three inches 

 broad. Inhabits the British coasts. 



Genus 59. — GALEOMMA.—Daudin. 



Generic Character. — Equivalve, inequilateral, transverse, 

 with a large oval gape at the front margin ; hinge without teeth, 

 ligament internal. 



Galeomma Twr/oni.— Turton's Galeomma. Plate XV. fig. 

 8. Tumid in the middle, and gradually sloping to the sides ; 

 dull milk-white, covered with short interrupted opaque lines ; 

 beaks prominent and central. Breadth nearly an inch. Inha- 

 bits the English channel. 



Genus 60.~MAGDALA.— Zeac/i. 



Generic C/iaracfer.— Transversely oblong-ovate, gaping at 

 one end j beaks obtuse ; hinge without teeth, but provided with 

 a transverse unconnected plate, attached to each valve by a car- 

 tilage and an oblique descending groove ; cartilage internal. , 



Magdala striata The Striated Magdala. Plate XVIII. 



fig. 12. Ovate-oblong, thin, pellucid, white; posterior side 

 rounded and the anterior side truncated and gaping, with longi- 

 tudinal striae and concentric wrinkles ; inside pearlaceous. One 

 inch broad. Inhabits the British seas. 



Genus 61.— MYATELLA.— 5roM»tt. 



Generic Character. — Sub-parallelogram. ical, transverse, an- 

 terior end truncated ; the valves refleX;, forming a hiatus ; umbo 

 small, placed nearest the posterior end ; with one erect, broad, 

 doubly channelled tooth in the left valve, which locks into a 

 corresponding cavity in the other. 



