A 



( 44 ) 



(A ngyostoma ta .) 



16. Dolabella. Lam. Pi. 



13, fig. 6. 



Ditto, but base more Calcareous, 

 enlarged in proportion ; 

 summit more prolonged 

 and curved. 



dian Seas. 



V. Animal, p. 60. 



Marine. 



Mediterranean, In- 



17. PlEUROERANCHUS. CuV. 



An oval plate. 



Marine. 



V. Animal, p. 60. 



18. Planospirites. ( 1 ) 



Faujas. 



Sub-orbicular ; a spiral 

 cord-like ridge on the in- 

 ferior surface. PI. 1, fig. 



20. 



Maestricht. 



(1) This is one of the rarest and most singular shells found at Maastricht^ only 

 three having as yet been met with. It seems impossible to determine whether it is 

 an univalve or a bivalve ; for although it resembles the valve of an oyster in form 

 and thickness, it wants the little hollow found at the summit of that shell and 

 serving to lodge the ligament which characterises the genus ; neither has it any 

 apparent muscular impression. If it be a bivalve, it is nearest to the genus 

 Acardo of Lamark, but its spiral cord or ridge, with the absence of the hollow 

 and muscular impression, lead us to conclude that it is an univalve. 



