21 



TAB. CCCCXX. 



AMMONITES Catena. 



Spec. Char. Depressed, furnished with two 

 rows of short tubercles upon each side; 

 whorls 6 or 8 smooth, with flat sides, the 

 inner ones exposed ; front rather convex ; 

 aperture square. 



^o seldom is any more than the casts of the chambers 

 of this shell found that its true form is scarcely known ; 

 these casts have, by the decay of their surfaces, lost so 

 much that they hang loosely together, like the links of 

 a chain : when less diminished, they are found adhering 

 but with very slight traces of the shell remaining ; it 

 appears to he smooth, and to have no undulations or 

 ribs excepting when very young : the tubercles are 

 upon the inner and outer angles of the flat sides of 

 the whorls ; they are of a moderate size, conical, with 

 rounded points, and are not truncated in the cast : the 

 edges of the septa are very much, deeply and sharply 

 sinuated ; the front is slightly rounded, without any ap- 

 pearance of a keel. 



A long known, and highly admired relic of the ancient 

 world ; the casts of the chambers hanging loosely to- 

 gether have an imposing appearance. It seems that 

 this shell was first lined with a sparry crust, containing 

 much Iron, and afterwards filled up with crystallized 

 carbonate of Lime ; the shell and ferriferous lining being 

 very liable to decay, have generally disappeared, and 

 left the remainder of the cast in detached portions. The 

 most perfect specimen of this kind, is one in the pos- 

 session of our valuable and scientific Friend, James 



Vol. V. August, 1823. l / ^ 



