imperfectly -defined Species of Jurassic Nautili. 281 



toarcensis, d'Orbigny, but the latter is readily distinguished 

 by its much thicker and broader shell, larger umbilicus, and 

 more distant septa. 



It is often a matter of very great difficulty to identify the 

 species of Nautilus figured in the ' Mineral Conchology,' 

 owing partly to the brief descriptions and partly to the 

 figures being foreshortened, with the object of economizing 

 space by showing as much of the specimens as possible in 

 one view. Two views at least of each species are essential 

 in order to give a correct idea of the form of the shell. There 

 can be little doubt, however, that the specimens we have, after 

 very careful comparison, referred to N. obesus are identical 

 with Sowerby's fossil. Though the type specimen is unfor- 

 tunately not in the " Sowerby Collection," there is an 

 example in that collection labelled, probably by Sowerby 

 himself, U N. obesus" which sufficiently agrees with the figure 

 and description in the Min. Conch, to justify its reference 

 thereto. Besides this individual there are several others both 

 from England and France which, though young shells, 

 possess unmistakably the characters of the present species. 

 It is hoped that the figures here given of N. obesus may help 

 to make it recognizable. 



O ••IT** 



On comparing examples of this species from the interior 

 Oolite of Courcy, Normandy, witli d'Orbigny's figure of 

 Nautilus lineatus *, we find that they agree remarkably well, 

 and we have therefore placed the N. lineatus of d'Orbigny in 

 the synonymy of the present species. 



Horizon. Inferior Oolite. 



Localities. Bath, Dundry, Somersetshire; Minchinhamp- 

 ton, Gloucestershire : Courcy, Normandy. 



11. Nautilus inornatus, d'Orbigny. 



1842. Nautilus inornatus, d'Orbigny, Paleontologie Fran^aise, Terr. 



Jurass. vol. i. p. 152, pi. xxviii. 

 1845. Nautilus inornatus, Murchison, Outline of the Geology of the 



Neighbourhood of Cheltenham, new ed. p. 91. 

 1849. Nautilus inornatus, d'Orbigny, Prodr. de Paleont. Stratigr. 



vol. i. p. 245. 



1857. Nautilus inornatus, Etheridge, in Mem. Geol. Surv. Great 

 Britain ; Hull, On (lie Country around Cheltenham, p. 27. 



1858. Nautilus inornatus, Ooster, Cat. dea Cephalopodes Fossiles des 

 Alpes Suisses, pt. iii. p. 8. 



18tx>. Nautilus inornatus, Day, Quart. Journ. Geol. Soc. vol. xix. p. 291. 

 18(34. Nautilus inornatus, Eudes-Deslongchamps, Etudes sur le.s Etages 

 J urascsiques Inferieurs de la Norniaudie, p. 83. 



* Paleont. Franc., Terr. Jurass. vol. i. p. 155, pi. xxxi. figs. 1, 2. 

 Aim. & May. N. Hist. Ser. 6. Vol. v. 21 



