34 



16. Belemnites, Lister, 1678 



= Belemnitis lapis, Agricola, 1546. 

 = Belemnites, Gesner, 1565. 

 =Acamas, Montfort, 1808. 

 = Hibolithes, Montfort, 1808. 

 = Thalamus ( = alveolus, &c), 1808. 

 = Actinocamax, Miller, 1823. 

 =Pseudobelus, Blainville, 1827- 

 = Belemnosepia, Buckland, 1836. 

 =Belopeltis, Voltz, 1840 (a pro- 



ostracum). 

 =Notosiphites, Duval- Jouve, 1841. 

 = Gasterosiphites, „ „ 



17. Belemnitella, D'Orbigny, 1840 ... 



18. Belemnoteuthis, Pearce, 1842 ... 



=Keloeno, Munster, 1836. 



= Acanthoteuthis, Munster, 1839. 



=Plesioteuthis, Wagner, 1860. 



19. Conoteuthis, D'Orbigny, 1840 ... 



20. Xiphoteuthis, Huxley, 1864 



= Orthocera (pars), De la Beche, 

 1829. 



Shell (guard) straight, generally long, 

 somewhat cylindrical, conical below, 

 with a hollow cone (alveolus) in the 

 upper part, containing a chambered 

 cone (phragmocone), which has a mar- 

 ginal canal (siphuncle) ; the thin, shelly 

 covering (conotheca) investing the 

 chambers, prolonged on one side into a 

 broad lobe (pro-ostracum, pen) ; animal 

 not clearly known, double rows of 

 hooks on the arms ; from Liassic into 

 Cretaceous formations. 



Shell (guard) in its highest part, marked 

 by a short longitudinal slit ; Cretaceous. 



Shell consisting of . a chambered cone, 

 having at its upper part a horny pen 

 with thin side bands, and at its lowest 

 part a thin fibrous guard, with two 

 diverging ridges ; animal with arms and 

 horny hooks, fins large ; Oolitic. 



Chambered cone slightly curved, pen elon- 

 gated and very narrow ; Cretaceous. 



Shell cylindrical ; chambered cone long 

 and narrow ; pen very long and slender, 

 section an ellipse ; Liassic. 



Second Order. — Tetrabranchiata. 



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

 generally subcentral ; the edges of the partitions (septa) which 

 separate the chambers either without folds, or slightly undulating. 

 Family, Nautilid.e. Thirty fossil genera : Nautilus, Discoceras, 

 Ophidioceras, Gyroceras, Cyrtoceras, Cyrtocerina, Oncoceras, 

 Streptoceras, Piloceras, Lituites, Lituunculus, Orthoceras, Tre- 

 toceras, Huronia, Actinoceras, Ormoceras, Aulacoceras, Endo- 

 ceras, Cameroceras, Trochoceras, Hercoceras, Gomphoceras, 

 Phragmoceras, Ascoceras, Glossoceras, Aphragmites, Aturia, 

 Nothoceras, Bathmoceras, and Gonioceras. 



Division A. — Edges of septa without fold. 

 I. Shell spiral, in the same plane. 



21. Nautilus, Breynius, 1732 



= Nautilus, Belon, 1553. 

 =Planorbites, Lamarck, 1799. 

 =Angulithes, Montfort, 1808. 

 = Oceanus, „ „ 



= Ammonites (^ars),Montfort,1808. 

 = Bisiphites {pars), „ „ 

 = Conchyliolithus, Martin, 1809. 

 = Ammonellipsites, Parkinson, 1811. 

 =Ellipsolithes (pars), Sowerby, 

 1812. 



Turns (whorls) of the shell, in contact, 

 partially overlapping; siphuncle almost 

 central; aperture of exterior chamber 

 open, without folds; Silurian into 

 Tertiary, still living. 



