﻿62 BRITISH FOSSIL CEPHALOPODA. 



Group III. Spirales. 

 Genus Nautilus, antiquorum. 



1732. Nautilus, Breyn, 'Diss. Phys. de Polytbalamiis.' 

 1808. Bisiphites, Montfort, ' Concbyl. Systeme.' 



1832. Clymenia, Minister, 'Beitrage zur Petrefactenkunde ' [ = subgenus]. 

 1835. Aturia, Bronn, ' Letbsea Geognostica ' [ = subgenus]. 

 1838. Teocholites, Conrad, 'Ann. Geol. Eeport.' 

 1844. Temnocheilus, M'Coy, ' Syn. Carb. Foss. Ireland.' 

 — Discites, „ „ „ [ = subgenus]. 



1850. Cryptoceras (part), D'Orbigny, 'Cours de Pal. stratigraphique.' 

 1856. Nothoceras, Barrande, ' Bull. Soc. Geol. France' [ = subgenus]. 

 1861. Trematodiscus, Meek & Wortben, 'Proc. Acad. Soc. Pbiladelpbia.' 

 1865. Hercoceras, Barrande, ' Defense des Colonies.' 



History. — It is certain that both the shells which have been called Nautilus were 

 known to Aristotle ; namely, that which is now called by the same name in Zoology, 

 the " Pearly Nautilus," and that which has become the " Argonaut " or " Paper 

 Nautilus." Breyn, to whom we may look as the earliest systematic writer on 

 Cephalopods, made this a genUs, and the work of subsequent authors has been to 

 subdivide it into groups, which may be called genera or subgenera according to 

 taste. The Bisiphites of Montfort was merely an example which showed clearly the 

 usual small dorsal lobe in the septum, which was mistaken for a second siphuncle. 

 The subgenus Clymenia, founded by Miinster, has the best claims for generic rank, 

 by its open whorls, its siphuncle within the dorsal lobe, and its sometimes angular 

 sutures ; it is only the combination, however, of these characters that is peculiar. 

 Each may separately be matched in other groups. The tertiary Aturia of Bronn 

 is merely an involute Clymenia, showing the close connection of both with Nautilus 

 proper. Trocholites was founded in 1838 by Conrad in an inaccessible journal, but 

 obtained currency by Hall's description and figures in the ' Palaeontology, of New 

 York ;' it is merely a Nautilus, in which the siphuncle is contained within the dorsal 

 lobe. M'Coy, in 1844, proposed two subdivisions of the genus for Carboniferous 

 fossils : the first, Temnocheilus, being merely those whose apertures were well enough 

 preserved to show their sigmoid outline ; the second, Discites, was with more reason 

 adopted for open-whorled species, of which those with angular sections were after- 

 wards called Trematodiscus by Meek and Worthen. D'Orbigny created the genus 

 Cryptoceras, for the Nautili with external siphuncles found in the Carboniferous 

 rocks. Barrande gave the name Hercoceras to certain forms, of which some 

 belong to Nautilus, characterised by a shelly deposit in the region of the hood 



