>!8 



49. Gonioceras, Hall, 1847 Siphuncle marginal. Septa waved, shell 



compressed into an elliptic form ; Silu- 

 rian. 



IX. — Shell many chambered ; the last (exterior) chamber large ; sijjhuncle 



marginal ; the edges of the partitions (septa) which separate the 

 chambers, angulated or waved, but not dentated or foliated. 

 Family, Goniatid^e (Barrande, 1867). Three genera : Goniatites, 

 Clymenia, and Bactrites. 



1. Shell spiral in the same plane. 



.50. Goniatites, De Haan, 1825 The turns of the shell in contact, over- 



Nautilus, Lamarck, 1799. lapping; siphuncle near the outer 



Orbulites, „ 1801. (convex) side; edges of the partitions 



Aganides, Montfort, 1808. separating the chambers much waved, 



Nautellipsites, Parkinson, 1811. hut not having at their base small, 



Ellipsolithes {pars), Sowerby, 1812. convex, toothlike projections; from Si- 

 lurian into Trias. 



51. Clymenia, Munster, 1832. The turns of the shell in contact, over- 



= Endosiphonites, Ansted, 1840. lapping ; siphuncle near the inner (con- 



= Subclymenia, D'Orbiguy, 1850. cave) side; edges of partitions waved 



with slight angular depressions. (This 

 genus has affinities with Aturia, but 

 the turns of the shell are more over- 

 lapping in the latter, and the siphuncle 

 is larger). Devonian into Carboniferous. 



2. Shell straight. 



52. Bactrites, Sandberger, 1841. Siphuncle marginal; septa gently waved, 



= Stenoceras, D'Orbigny, 1850. a single angular depression (lobe) ; ex- 



= Trematoceras, Eichwald, 1851. ternal chamber not known ; from Silu- 



rian into Devonian. 



X. — Shell many chambered ; the last (exterior) chamber large ; siphuncle 



marginal ; the edges of the partitions (septa), which separate 

 the chambers, many-waved, with single circular or subcircular 

 depressions at their base. Family, Clydonitid^e. Four genera : 

 Clydonites, Choristoceras, Rhabdoceras, and Cochloceras. 



1. Shell spiral, the turns touching, in the same plane. 



53. Clydonites, Hauer, 1860 Triassic and Cretaceous. 



2. Shell spiral, the turns not touching, in the same plane. 



54. Choristoceras, Hauer, 1865 Triassic. 



3. Shell straight. 



55. Rhabdoceras, Hauer, 1860 Triassic. 



4. Shell spiral, the turns touching, not in the same plane. 



56. Cochloceras, Hauer, 1860 . ....... Triassic. 



XL — Shell many chambered ; the last (exterior) chamber large, siphuncle 

 marginal (dorsal) ; the edges of the partitions (septa), which 

 separate the chambers, waved, with many small circular eleva- 

 tions (crenulations) at the base of each wave. Ceratitid^:. 

 Two genera : Ceratites and Baculina. 



