22 
are often much distorted. They are in all these places ac- 
companied by various other shells, especially by Trigonia 
aliformis and two unpublished species of Rostellaria, 
which, as far as the very imperfect fragments hitherto 
obtained will indicate, are nearer allied to the R. Pes 
Pelicani, than they are to R. Parkinsoni. 
Since the Plate was engraved, we have met with a 
beautiful white individual of this species, from Black- 
down, in which the short, cylindrical, external ligament 
is very neatly cast in Silex. 
