CONCHOLOGY. 
jecting a little inwards in each valve and an 
additional moveable one in one of the valves : 
lateral teeth none. 
Includes Mya convexa, pubescens, declivis, 
pretenuis, distorta, striata, and Anatina truncata 
of Turton, 
21, Listera. Shell oval, equivalve, alittle open at 
the sides. Hinge with a spoon-shaped tooth, and 
additional small ones on one side ; lateral teeth 
none. 
Includes Mactra Listeri. 
22. Agina, Shell oval, equivalve. Hinge with a 
single erect somewhat cloven penetrating tooth in 
each valve : lateral teeth none. 
Includes Mya purpurea. 
23. Solen. Shell transversely lincar equivalve, 
inequilateral, open at both ends. Hinge near 
one end, with the beaks obscure ; teeth varying 
in number and shape: lateral ones none, 
-Includes Solen vagina, siliqua, ensis, and 
pellucidus. 
24, Psammobia, Shell transverse, oblong or oval, 
equivalve ; mostly open at the sides. Hinge 
with two teeth in each valve, one of them obscure ; 
lateral teeth none. 
Includes Solen fragilis, Ps. fiorida and costulata 
of Turton. S. legumen, strigilatus, antiquatus, 
and vespertinus. Venus deflorata. Tellina ferroen- 
sis, solidula. 
25. Tellina. Shell transverse or suborbicular, 
flattish, with a flexuous plait on the anterior side. 
