PLATE 6. 
of Linne) which they resemble in form and in the furrows 
of the surface. The want of the scales and processes, with 
which that species is roughened, was attributed to the 
specimens being merely nuclei, or casts, consequently retain- 
ing only the internal shape of the original. An attention to 
this fossil, whenever opportunity offered it for observation, 
has induced me to alter this opinion. I am inclined now 
to believe, that all the specimens I have yet seen, display 
the external surface and marks of their prototype, and that 
this is not any species of Pinna, at present known in a 
recent state. 
