THE CEPHALOPODA. 



193 



XH. Flexuosi.' — Tubercles are developed on both sides of the siphonal area, which 

 is not sunk flat between two rows of a depressed surface, but is elevated therefrom and 

 divided by a continuous row of tubercles. The radii on the sides are strongly bent 

 forward towards the margin. They are, in general, divided, and here form long knobs, 

 which are somewhat elevated at the lower part of the lateral surface. The siphonal lobe 

 is much shorter than the upper lateral. They are special to the Upper or White Lime- 

 stone of the Jurassic formation of Germany, and are found, likewise, in the Lower 

 Chalk. The following are typical species : 



Fig. 72. — Coamoceras Duncani, Sow. 



Cosmoceras flexuosus, Munst, 

 — Jason, Rein. 



Fig. 73. — Cosmoceras radiatus, Brugiere. 



Cosmoceras radiatus, Brugiere (fig. 73). 

 Hoplites falcatus, Mant. 



Professor Quenstedt in 1849 published an important work on the Cephalopoda, 

 together with an atlas of beautiful plates,^ in which he divided the Jurassic Ammonites 

 into fourteen groups, retaining those so well established by von Buch, and adding four 

 more to the list : 



1. Arieten. 



2. Capricornen. 



3. Amaltheen. 



4. Heterophyllen. 



5. LiNEATI. 



6. Palciferen. 



7. Disci. 



8. Denticulaten. 

 y. Ornaten. 



10. Dentaten. 



11. Planulaten, 



12. coronaten. 



13. Macrocephalen. 



14. Armati. 



and divided the Ammonites from the Chalk formations as follows : 



15. Cristati, d'Orhigny. 16. Rhotomagenses, d^Orhigny. 



17. LiGATi, d'Orhigny. 



and classed the Ammonites of the Red Alpine Limestone (Triassic), distinguished by 

 Terebratula diphya as : 18. Globosi, Quenstedt. 



1 ' Petrefactenkunde Deutschlands : der ersten Abtheilung, die Cephalopoden,' 8vo., nebst einen Atlas 

 von 36 Tafeln, fol. Tiibingen, 18-19. 



