GEOLOGY OF FOLKESTONE — THE GAULT. 



395 



and Lamark, who of course classed tliem with the cephalopods ; Par- 

 kinson, who considered their spathose structure as due to fossil- 

 ization ; Schlotheim, Ferussac (1822) and J. S. Miller, who in 1823 

 read a paper before the Geological Society of London, specifying the 

 nature of the Belemnite and its position in the animal, considering it 

 analogous to the bone of the sepia, but according that priority of in- 

 formation which was due to M. de Blainville. 



We now hand our readers a list of the classification of the cepha- 

 lopods, and shall then proceed to describe more particularly the 

 natural characters of the divisions which are essential for a proper 

 knowledge of the beautiful fossil forms of the Gault. 



CLASS, CEPHALOPODA. 



Order 1. — Dibranchiata = Acetabulifera. 

 Section L — Octopoda = 8 arms. 



Family 1. Argonautidce. 



2. OctopodidcB. 



Section II. — Decapoda. 



3. Teuthidce. 



4. Belemnites. , 



5. SepiadcB. 



6. Spirulidce. 



Order 11. — Tetrabranchiata = Tentaculifera. 

 Section I. — Nautili. 



Family 1. NautilidcB. 



2. OrthoceratidcB. 



Section II. — Ammonites. 



3. Ammonitidoe. 



Where the ornamentation of a class of shells is so various and in-^ 

 tricate as in the Ammonites, it becomes necessary to classify, as far 

 as possible, the general characters of the hinds of patterns or methods 

 on which the ornamentations are based. In the Ammonites these 

 variations are at once apparent and distinct ; we see some with keels ; 

 some with channels, or furrows along the back ; some with the backs 

 square ; some round ; some sharp and others crenated ; and these 

 again in varied stages, and susceptible again of minor divisions. 

 Quenstedt, whose work is generally taken as the basis of the classi- 

 fication of the Ammonites, has thus divided them — an arrangement 

 which has been adopted by Mr. S. P. Woodward. 



