37 



hinge central, with a single tooth in one valve (some- 

 times a second rudimentary one) and two in the other, 

 behind which the margin is callous. 1...2. Rare. 



S. DECLIVIS. Turt. Con. Die. p. 164. t. 22. /. 80. 

 F. p. 460. List. t. 321. Oblong, rounded at the 

 extremities, dorsal margin slightly convex, ventral 

 straight; thin, semi-transparent, with a dark brown 

 cuticle, irregularly and concentrically striated, beaks 

 subcentral; sloping gradually to the extremities; 

 slightly indented before the beaks; teeth strong, two 

 in each valve, one of them concave and in one valve 

 one is oblique, behind which the margin is callous. 

 I...2. Stilly Isles. 



S, FRAGILIS. Pult. Dor. p. 28. Mont. p. 51. 



P.p. 460. PSAMMOBIA TffiNIATA. Turt. B.p. 85. 



Oblong, rounded at the extremities, a little contracted 

 in the middle, dorsal and ventral edges subparallel, 

 thin, transparent, smooth, with a greenish cuticle, some- 

 times marked with a longitudinal reddish stripe from the 

 hinge towards the ventral margin; beaks subcentral; 

 in one valve two erect teeth, one of which is pointed the 

 other with one subulate tooth: an internal longitudinal 

 rib. ...0,95. 



