128 



quivalve, occasionally gaping a little at the posterior 

 side; never attached toother bodies by the lower valve, 

 though often found enveloped in sponge or marine fuci. 

 The interior of the valves is pearly, and their substance 

 solid, and sometimes semitransparent. 



Lamarck does not mention that the exterior of the 

 valves, particularly the upper one, is armed with finely 

 granulated or striated longitudinal rays, extending from 

 the apex to the margin, and with one lengthened mus- 

 cular impression within each valve. 



Vulsella lingulata Vulsella spongiarum 



hians mytilina 



rugosa ovata 



[And one fossil species.] 



PLACUNA. 



ANOMIA SELLA. Linn. 



Mawes Linn. pi. \bjfiy. 1. 

 The very peculiar form of the hinge in the shells of 

 this genus, which on one valve is that of the letter V, 

 the lower parts not quite joined together, with corre- 

 sponding cavities on the other valve to admit them, and 



