216 THE LIAS AMMONITES. 



7. Shell spiral, not in the same plane. 



68. TuRRiLiTES, Lamarck, 1801. = Turrites, de Haan, 1825. = Turrilitlies, 



Bronn, 1833. 



Turns of the shell spiral, in contact ; Oolitic into Cretaceous. 



69. Helicoceras, d'Orbigny, 1840. = Helicocerus, King, 1844. 

 Turns of the shell spiral, not in contact ; Oolitic into Cretaceous. 



8. Shell forming straight and curved lines, not in the same plane. 



70. Heteroceras, d'Orbigny, 1850, 



Turns of the shell at first spiral and in contact, not in the same plane, afterwards 

 tangentially divergent, finally recurved and not in contact, and produced at a different 

 angle to that of the spiral ; Cretaceous. 



71. Anisoceras, Pictet, 1854. 



Turns of the shell at first spiral, not in the same plane, next tangentially divergent, 

 and finally recurved, none of the turns in contact ; Oolitic into Cretaceous. 



