THE APTYCHUS. 11l 
On Ihe Aptychusn. 
BY MR. CHARLES MOORE. 
N the present advanced state of scientific knowledge, it 
does not often happen that any objeetin Natural History 
remains long, without being assigned its position in the 
animal kingdom. This however has not been the case 
with a curious body called the Aptychus, respecting which 
there have been various speculations. For some time it 
was supposed to belong to the Cirripides. Professor Forbes 
refers it to the Holothuriad& ; and Mr. Strickland, in a 
paper read on this subject before the Geological Society of 
London, believes it to belong to the ammonite, to which 
shell he considers it an operculum ; or else, he suggests that, 
like the Nautilus, the animal of the Ammonite may have 
required horny supports, and that these bodies may have 
performed that oflice. 
It has been noticed that the Aptychus is rarely found 
except in beds of the secondary formations, in which 
the ammonite is obtained ; consequently it has not been 
obtained higher than the chalk, in the beds above which 
the ammonite is supposed to have become extinct, and not 
