22 



Clealand, Esq, there is also a very good one in the 

 British Museum ; the former is selected for a figure. I 

 have one that exhibits a near approach to the external 

 form of the shell, but would not make so handsome a 

 figure ; it has in one part a small portion even of the 

 shell itself remaining; none of its joints are free : on 

 one side of it are several young Oysters, and on the 

 other, a full grown Oyster, (Ostrea Delta) they adhere 

 so closely, that there does not appear to be space enough 

 between them and the stony cast for any shell, it 

 must have been thin, and is perhaps of such a texture 

 as does not permit it to be readily distinguished from 

 the Oyster ; or we must conclude that the Ammonite 

 was in a fossil state before the Oysters existed, but had 

 not been removed far from its original station, before it 

 was again buried to form along with the Oysters the in- 

 dex to another epocha. This is the species referred to 

 at page 72 of Vol. IV. as resembling the A.perarmatus. 



Found imbedded in sand in Marcham Field, near 

 Abingdon, in Berkshire ; parts sometimes occur that 

 must have belonged to shells above a foot in diameter. 



Casts of A. perarmatus tab. 352, in a similar loose 

 state of preservation, are found accompanying the A. 

 catena, and until lately, have been confounded with it : 

 the ribs that connect the tubercles in pairs will distin- 

 guish them ; such ribs being very rare upon the smaller 

 spined A. Catena. 



