4 
large shells, for some individuals, that appear to be of a 
more luxuriant growth than others, are thin in the mid- 
dle. 
Since this curious shell was discovered by M. Defrance, 
attached to a fragment of an Inoceramus* Cuvieri, it has 
been repeatedly sought for ; at length Mr. G. B. Sovverby 
was fortunate enough to find the attached valve upon 
an Echinus in Chalk ; its cellular structure was then 
noticed as a character by which to distinguish it from 
other attached shells, and numerous specimens have been 
met with upon Echini, Inocerami, and other shells found 
in Chalk, in various parts pf England. The upper valve 
had still remained unknown, had it not been accidentally 
discovered almost concealed in chalk upon a dislocated 
Echinus, picked up at Brighton several years ago, by 
G. B. Snow, Esq. : this is shewn in the upper figure. 
The lower figure shews three states of the attached 
valve, found upon an Echinus sent from Norfolk by the 
Rev. G. R. Leathes. 
^ This Generic name will probably be superseded. 
