55 



ing slightly at the sides, they have not the irregular 

 plait on the anterior part, though they sometimes have 

 a symmetrical angle or pinch on that side, in each 

 valve. Shell elliptical, transverse, or a flattish oblong 

 oval, slightly gaping: apices projecting. Hinge with 

 two teeth on the left valve, and one only inserted on 

 the opposite. 



Psammobia virgata Psammobia alba 

 Ferroensis Cayennensis 



vespertina 



florida 



maculosa* 



caerulescens 



elongata 



flavicans 



squamosa 



laevigata 



tellinella 



pulchella 



aurantia 



fragilis 



livida 



Galathea. 



PSAMMOT^A. 



These shells are only degenerated Psammobiae; they 

 no longer have three cardinal teeth, (two on one valve 

 and one on the other), as the left valve of the Psam- 

 motaea only presents one tooth, and sometimes one 

 of the valves is without a tooth, the other exhibiting 

 two. Shell transverse, oval, or oblong ; gaping a little 



