imperfect] i) -defined Species of Jurassic e&e. Nautili. 403 



tion of its siphuncle, somewhat larger umbilicus, and tn>re 

 inflated whorls. 



The gradual shifting of the position of the siphuncle in the 

 present species from a central position in the young to a nearly 

 external position in the adult is a feature met with in other 

 species ; Stoliczka has observed it in Nautilus Huxley mus, 

 Blanford, and in N. sjykwricus, Forbes, and other species *. 



Many authors have recorded the occurrence of various 

 species of Nautilus in the lied Chalk or Hunstanton Lime- 

 stone f ; but the present form does not appear yet to have 

 been characterized. 



Horizon. Red Chalk. 



Locality. Hunstanton, Norfolk. 



8. Nautilus triangularis, Montfort. 



1802. Nautilite triangulaire, Montfort, in his edition of Sonnini's 



" Suite a Button " (Hist. Nat. des Mollusques, An. x.), vol. iv. p. 292, 



pi. xlix. tig. 2. 

 1808. Nautilus triangularis, Montfort, Conch. Syst. p. 7 (G. angu- 



lithes). 

 1820. Nautilites angulites, Schlotheim, Die Petrefactenkunde, p. 84. 

 1832. Nautilus triangularis, Passy, Descr. Geol. de la Seine-Inferieure, 



p. 334. 

 1834. Nautilus triangularis, d'Archiac, Mem. Soc. G6ol. de France, 



vol. ii. pt. ii. p. 191. 

 1840. Nautilus triangularis, d'Orbigny, Paleontologie Francaise, Terr. 



Cret., vol. i. p. 79, pi. xii. 

 1842. Nautilus triangularis, Matheron, Cat. M£th. et Descrip. des Fos- 



siles du Depart, des Bouches-du-Rhone et Lieux Circonvoisins, 



p. 259. 

 1850. Nautilus triangularis, d'Orbigny, Prodrome de Paleontologie 



Stratigraphique, vol. ii. p. 145. 

 1852. Nautilus triangularis, Giebel, Fauna der Vorwelt, Band iii. 



Abth. i. p. 162. 

 1854. Nautilus triangularis, Millet, Paleontologie de Maine et Loire, 



p. 103. 



* Mem. Geol. Surv. India, Palseont. Indica, ser. iii. 1866, p. 205. 

 t The following are some of the principal references : — 



(1) Samuel Woodward, ' An Outline of the Geology of Norfolk,' 

 1833, p. 54. — Nautilus elegans. 



(2) Rev. Thomas Wiltshire, " On the Red Chalk of England," Geol. 



Assoc. 1859, p. 17, pi. i. fig. 3. — Nautilus simplex. 



(3) H. G. Seeley, " Notice of Opinions on the Stratigraphical Position 



of the Red Limestone of Hunstanton," Ann. & Mag. Nat. Hist, 

 ser. 3, vol. vii. 1861, p. 244. — Nautilus simplex. 



(4) Rev. T. Wiltshire, " On the Red Chalk of Hunstanton," Quart. 

 Journ. Geol. Soc. vol. xxv. 1869, p. 185. — Nautilus albensis, N. 

 Bouchardianus. 



(5) W. Hill, " On the Lower Beds of the Upper Cretaceous Series in 

 Lincolnshire and Yorkshire," Quart. Journ. Geol. Soc. vol. xliv. 

 1888, p. 347. — Nautilus, sp. 



