6 ) 



4. P anopsia. Menard. M. 



Equivalved, transverse, 

 unequally gaping at the 

 sides. Fig. 9. 



5. Psammobia. Lam. M. 



Oblong -oval, rather 

 flat, a little gaping on 

 each side. Beaks more 

 projecting. Fig. 10. 



6. Psammotea . Lam. M. 



Oblong-oval, a little 

 gaping at the sides. Beaks 

 more projecting. The in- 

 ner, callous, edsjes project- 

 ing a little. (2) Fig. 11. 



One conical cardinal 

 tooth on each valve, and 

 a compressed callosity 

 at the side, not project- 

 ing without. 



Hinge with 2 teeth on 

 one valve, and 1 on the 

 opposite valve, entering 

 between the other two 

 when closed. 



1 cardinal tooth on 

 each valve, or on one 

 valve only. 



Ligament exterior, on 

 the longest side of the 

 shell ; fixed on the cal- 

 losities. (1) 



Ligament exterior. 



Ligament 



exterior, 

 attached to the inner, 

 callous, edges. 



DIVISION IV. 3MYAR1.E. 



GENERA. 



i. Mya. Lin. M. 



Shell gaping at each A large compressed, Ligament interior, in- 

 end. Fig. 12. rounded, cardinal tooth, serte'd on the tooth and 



projecting almost verti- in the hollow. (3) 

 cally, and hollowed like 

 a spoon. A cardinal hol- 

 low' on the other. 



2. Anatina. Lam. M. 



Sub-equivalved, gaping 

 at both ends, or at one 

 only, Fig. 13. 



A tooth like that of 

 the Mya on each valve, 

 the teeth supported ei- 

 ther by a rib or a plate 

 running obliquely into 

 the shell, and frequently 

 a decurrent fissure giving 

 the appearance of a se- 

 conJ plate. 



Ligament interior, at- 

 tached to each tooth. 



(1) Mediterranean. Foss. at Parma. The species found at the foot of the Appe- 

 nines is in such good preservation that it appears as if justtaken from the sea. 



(2) Lamarck supposes this genus to be composed of degenerated Psammobia, 

 Foss. at Grignon. 



(3) Foss. in the London Clay, Crag Marl) FFoolwich Loam, and Green Sand, 

 Fuller' 's-earth Rock. 



