362 
XAUTILOIDEA. 
D'Orbigny i was the first to refer some of these fossil Cej)halo- 
podous beaks to the genus Nautilus, from their resemblauce to 
those of the recent animal. He remarks that Faure-Jiiguet, who 
gave them the generic name of IVujncholites, expressed no opinion 
as to their being the mandibles of Cephalopods, nor as to what 
animal they may have belonged to. M. Gaillardot, in 1824 (Ann. 
des Sci. Xat. vol. ii. p. 485), adopted the opinion of Guettard, who 
considered them to be the mandibles of an animal allied to Sepia. 
But this opinion was disputed by d’Orbigny for the obvious reason 
that the beaks of Sepia and of other Cephalopods without chambered 
shells are corneous, Avhereas the fossil beaks are “ always thick, full 
of calcareous matter, and of a different form.” 
Finally d’Orbigny separated the fossil beaks of Cephalopods into 
two groups, placing those of a triangular form, and concave beneath, 
in Blainville’s genus Conchorhi/nchus ; while for the wide and com- 
pressed forms he created the genus ItJninchoteuthis, rejecting the 
name liJufucholites as being “ too vague and often api)lied to the 
Echinids,” indicating only a “ fossil beak, which might as well be a 
beak of a Balanus, or that of a Bird.” He combats the idea ex- 
pressed by M. Doshayes (Encycl. Meth., art. Lechi, vol. iii. p. D44) 
that a generic name cannot bo properly applied to a mandible, 
which is only a ])art’ of the animal, by observing that upon such a 
principle it would be necessary to suppress half the fossil genera 
described, when only part of the organism is known, as in the case 
of Belemnites, and even all the Mammalia and Mollusca, the animals 
of which can never be known. On the contrary, d'Orbigny holds 
that all fossil remains that cannot be referred to any known genera 
should be placed as genera in whatever animal series they approach 
nearest to. 
This is sound reasoning if applied to Palaeontology in a general 
sense : but in this particular instance its application is rendered 
difficult by the want of stable characters upon which to found 
genera and species of fossil beaks. Xor is the material sufficiently 
abundant to enable one to trace the variations that may arise in 
different stages of growth, and thus to afford data for the limitation 
of such species as may be constituted. Ender these circumstances 
I have merely figured some of the principal types of the fossil beaks 
^ Mollusques Yivants et Fossiles, 1845, vol. i. p. 587. The figures which 
should have accompauied this volume were never published. 
- Loc. cit. p. 588. Extract from Ann. des Sci. Aat. 1825, vol v., Juin. 
