>'AriiLiDj:. 
16L 
angular margin and very steep sides. The septa are somewhat 
approximate, being about 5 lines apart upon the sides of the shell, 
where the ventro-dorsal diameter is about 2 inches. The sutures 
form a shallow backwardly-direeted sinus upon the sides and 
periphery. The body-chamber occupies about half of a volution. 
The aperture is deeply emarginate upon the peripheral side. The 
siphuncle is situated a little below the centre. The test, judging 
by fragments of it, is ornamented only with lines of growth which 
from a deep sinus upon the peri])hery, corresponding with the 
emargination of the aperture. 
Remarks. Some authors have adopted Eeinecke’s name arietis for 
the present species, on the ground of its priority over SchlotheinTs. 
The former, however, is very incompletely characterized, while the 
name lidorsatus bestowed upon this species by Schlotheim has 
become so thoroughly engrafted in palaeontological literature that 
it would only be an act of pedantry to change it, merely on the 
ground of priority, for a name which has not obtained currency. 
Professor Quenstedt * has attempted to show that Nautilus arietis, 
Pteinecke, differs from N. lidorsatus, Schloth., in the aperture being 
higher than wide ; but this is doubtless an error, probably arising 
from some mistake in measurement, for there seems nothing to 
distinguish Ileinecke’s figure in this respect from those of other 
authors (making allowance for the foreshortening of the drawing). 
Schlotheim figures one of the septa, seen in section, and this 
distinctly shows the superiority of the width over the height of the 
whorls, and the difference would be even greater were it not that 
one side of the specimen figured appears to have been somewhat 
crushed. 
Quenstedt distinguished two varieties Nautilus lidorsatus dolo- 
miticus{=N. lidorsatus, auct.), and Nautilus lidorsatus nodosus, 
Munster. I regard these as distinct species, though Giebel ^ places 
the latter in his synonymy of N. arietis { = N. lidorsatus). 
There is a fine specimen of the present species in the British 
Museum (registered iS'o. 36478) which shows the sinus in the 
aperture. The greatest diameter of this specimen is 7^ inches. 
In describing a species from the Salt-Bange of India — Nautilus 
latissimus, MTaagen — Dr. Waagen^ observes: — “The full-grown 
^ Petrefactenkunde Deutschlands, 1849, Band i. Abth, i. Cepbalopodeu, 
p. 54. 
^ Fauna der Vorwelt, 1852, Band iii. Abth. i. p. 157. 
^ Mem. Geol. Surv. India, 1879 — Palseont. Indica — Ser. xiii. Salt-Eange 
Fossils, Yol. i. Productus-Limestone Fossils, p. 58. 
PART II. 
