372 
NAUTILOIDEA. 
Remarhs. This type of mandible departs in no essential feature 
from that of the Cretaceous, except that the posterior portion is 
somewhat shorter than it is in the generality of Cretaceous forms. 
The present form bears some resemblance to one described and 
figured by Bellardi ^ from the Middle Miocene of Piedmont under 
the name of Rhy'ncholithes Allionii^ but the proportions of the two 
are different. 
JuEASSIC AND CkETACEOUS ManDIBLES OE UnCEKTAIN 
Affineties. 
The mandibles above figured (figs. 78-83) bear such a close 
resemblance to those of the recent Nautilus {N. pompilius) (figs. 
76, 77) as to justify their reference to the latter with a considerable 
measure of certainty But there are other mandibles in the Col- 
lection of a totally distinct type from any of those I have figured, 
and therefore it may be fairly concluded that they do not belong to 
the genus Nautilus ; but whether they belong to Ammonites or 
Eelemnites, or to non-testaceous Cephalopods, there is, at present, no 
evidence to show. 
The following types of mandible are more or less satisfactorily 
determinable : — Rhynchoteuthis Qaenstedfi, Coster This type of 
upper mandible is recognizable as one of the two or three distinct 
forms figured by Quenstedt in his ‘ Petrcfactenkunde Dcutsch- 
lands ’ all of which he erroneously referred to the RhyncholitJies 
acutus of Elainville®. Subsequently Coster in 1857 (loc. cit.), 
selecting one of the forms figured by Quenstedt (Petref. Deutschl. 
^ I Molluschi dei Terreni Terziari del Piemonte e della Liguria, 1872, pt. i. 
p. 22, tav. iii. fig. 2, a-c. 
^ The form (fig. 79, e-y) referred to Bhynchoteiithis quinqiiecarimtus should 
perhaps be excepted, as also fig. 81. Both these possess in the sharp keel on 
the inside of the upper mandible a character which distinguishes them very 
markedly from the other forms figured. 
^ Catalogue des Oephalopodes Fossiles des Alpes Suisses, pt. ii. 1857, p. 5, 
tab. iv. figs. 15, 16. 
^ Petref. Deutschl. 1816-1849, Abth. i. Band i. Cephalopoden, p. 547, 
tab. xxxiv. figs. 16, a, b, but not figs. 17, 18, 19. 
® Mem. sur les Belemnites, 1827, pi. v. figs. 22, 22 a, 22 b (Ehynchohthe 
aigu). Neither of the forms figured by Quenstedt agrees with Blainville’s, 
which is, however, a not very clearly marked form. D’Orbigny (Moll. Viv. et 
Foss. vol. i. 1845, p. 695) makes it a synonym of his Rhyncoteuthis Emerici, 
