60 CONCHOLOGY. 



3. Cypricardia. Four species. 



Distinguished from the Cardita by having three teeth be- 

 neath the apices, and a callous lengthened tooth or ridge. 



Shell obliquely elongated, equivalve, inequilateral ; valves 

 striated, but never ribbed ; hinge with three teeth beneath 

 the umbo, and one lateral elongated tooth. 



Cypricardia Guinaica. Cypricardia rostrata. 



C, angulata. C. coralliophaga. 



C. Guinaica. The Guinea Cypricardia. PI. 10, fig. 6. 



Species elongated, very inequilateral ; summit rounded 

 and recurved anteriorly ; two short divergent cardinal teeth, 

 besides a lamellous tooth ; ligament very long, projecting or 

 not ; yellowish white, covered with decussated striae. 



4. Hiatella. Two species. 



Established by Daudin ; classed by Linnaeus with the So- 

 len, but Lamarck is of opinion that it more nearly approxi- 

 mates the Cardita. 



Shell thin, sub-rhomboidal, equivalve, very inequilateral, 

 gaping at its inferior margin and posterior extremity ; the 

 summit very anterior and recurved in front ; dorsal hinge 

 formed by a single tooth on one valve corresponding to a 

 semicircular slope on the opposite valve, or by a small tooth 

 with a cardinal cavity in each valve ; ligament probably ex- 

 terior and dorsal ; muscular impressions unknown. 



Hiatella Arctica. Hiatella biaperta. 



H. Arctica. The Arctic Hiatella. 



Shell small, transversely oblong ; apices truncated, with 

 two divergent spring ridges ; a small tooth on each valve ; 

 cream colour, with decussated striae ; inside pearly. 



H. biaperta. The double-clefted Hiatella. PI. 10, fig. 4. 

 Species that has only a single tooth on one valve ; yel- 

 lowish white. 



