214 CONTRIBUTIONS 



ROTELLA. Lamarck. 



R. nana. Plate 6. Fig. 225. 



Description. Shell orbicular, flattened above, smooth, 

 margin rounded ; substance of the shell rather thin ; spire 

 nearly concealed ; outer lip sharp ; callus impressed in the 

 centre, bounded by a fine impressed line ; mouth nearly 

 round. 



Length l-20th, Breadth nearly .1, of an inch. 



St Mary's, Maryland. John Finch. 



The smallest figure is of the size of nature. 



Observations. This very minute Rotella is very much 

 flattened above, and the last whorl nearly covers over the 

 spire. The number of whorls is doubtful ; perhaps they 

 do not exceed three. The margin is rounder than usual 

 in this genus. A single specimen only has been observed 

 by me, and this was discovered in the sand, taken from the 

 cavity of a larger shell. 



I am not aware that the genus Rotella has before been 

 observed in a fossil state, in this country or in Europe. 

 M. Deshayes gives in his Tertiary Tables four recent spe- 

 cies, but none fossil. 



