THE CEPHALOPODA. 215 



2. Shell spiral, turns of the shell not in contact, in the same plane. 



60. Crioceras, d'Orbigny, 1840. = Crioceratites, Leveille, 1837. :^ Tropaeum, 



Sowerby, 1840. 

 Cretaceous. 



3. Shell an arc of a spiral, in the same plane. 



61. ToxocERAS, d'Orbigny, 1840. 

 Prom Oolitic into Cretaceous. 



4-. Shell changing from a spiral, in the same plane. 



62. ScAPHiTES, Parkinson, 1811. 



Turns of the shell at first spiral, in contact, and overlapping, afterwards tangentially 

 divergent ; finally recurved and not in contact ; Cretaceous. 



63. Ancyloceras, d'Orbigny, 1840. 



Turns of the shell at first spiral, not in contact, aftervi^ards tangentially divergent ; 

 finally recurved, and not in contact ; from Oolitic into Cretaceous formations. 



5. Shell forming straight and curved lines, in the same plane. 



64. Ptychoceras, d'Orbigny, 1840. = Ptychocerus, King, 1844. 



The shell at first straight, afterwards curved, and next straight, the turns in contact ; 

 Cretaceous. 



65. Hamites, Parkinson, 1811. = Baculita, Fleming, 1828. = Toxerites, 

 Rafinesque, 1819. 



The shell at first straight, afterwards curved, and next twice repeating the process ; 

 the arrangement forming a species of compressed spiral ; the turns not in contact ; 

 Cretaceous. 



66. Hamulina, d'Orbigny, 1850. 



The shell at first straight, afterwards curved, next straight ; the turns not in contact ; 

 Cretaceous. 



6. Shell forming a straight line. 



67. Baculites, Lamarck, 1801. ^ Homaloceratites, Hilpsch, 1781. = Tiranites, 



Montfort, 1808. 



The shell slightly conical; Cretaceous. 



