6^, ] CO^GEYLI A— DITHYRA. 21. 



Shell flat, nearly orbicular, equivalve, inec[uilateral, a little open 

 at the sides. Hinge of one valve with a single tooth and a trans- 

 verse linear lateral one each side ; of the other valve with a cavity 

 in the middle and a tranverse deeply cloven lateral tooth each side 

 the segments of which divaricate from the beak. Ligament 

 internal. 



Montagu had seen only one valve of this extremely rare and 

 valuable shell, and was consequently unacquainted with the whole 

 of the internal structure. 



In one of the valves is a central erect primary tooth between two 

 hollows ; and on both sides from the hinge runs a nearly straight 

 transverse rib a little within the margin, upon each of which is 

 jilaced a small tooth-like prominence not very remote from the hinge; 

 the rib also on one of the sides is furnished with a small internal 

 oblique cavity, not unlike the spoon-shaped tooth of the Anatina 

 convexa. 



In the other valve there is no primary tooth, but a large triangu- 

 lar cavity for the reception of the tooth of the opposite valve : and 

 the lateral teeth are transverse and divided from their origin, form- 

 ing acute angles, the points of which are close to the cardinal cav- 

 ity, with the inner limb continued by a rib like that in the opposite 

 valve. 

 squamosum. Lepton testd squamoso-punctatd. 



Shell punctured in a scale like manner. 



Tab nost. 6, fig. 1 to 3. 

 Solen squamosus. onfajrw, Test. Brit. p. 365. 



Linn. Truna. viii. p. 48. ' ^ 



