SECTION VIII. 167 



Seftion V. x\mmon*ia with a prominent 

 ridge, not plain as in Section III. but 

 wreathed or twifted like a rope : Ammo- 

 nia limbo tasniolato. 



Sedion VI. Ammonia with a plain fur- 

 row or channel along the back : Ammo- 

 nia fulco unico per dorfum duclo. 



Seftion VII. Ammonia vvhofe backs are 

 ftudded or fpiked: Ammonia dorfo tuber- 

 culato vel aculeate. 



Seftion VIII. Ammonia whofe backs 

 are deeply notched or toothed like a faw : 

 Ammonia dorib dentato. 



Genus 5. Ammonoides. The definition 

 of this genus is, that, in all other reipeds 

 except fliape, it refembles the Ammonite ; 

 for thefe bodies are quite globofe like Nau- 

 tili, and not flat like Ammonitas. The 

 outer Ipire alone makes above one half of 



M 4 the 



