152 
NAUTILOIDEA. 
1873. I^autilus (Temnocheilus) Jatus, Meek and Wortlien, Geol. Surv. 
of Illinois, vol v. Palaeont. p. G08, pi. xxx. ff. 2«, 2 b. 
'iNot 1878, Nautilus latus, de Koninck, Faune du Calcaire CaiFonifere 
de la Belgique (Annales du ]\Lus. Roy. d’Hist. Nat. de Belgique, 
tom. ii.), pt. i, p. 116, pi. xxiv. ff. ^a, 3 b, 3 c.] 
Sj). Char. Shell thick, disciform, composed of about two and a 
half or three volutions, very slightly embracing, and all exposed, 
forming a very largo umbilicus, with apparently a large central 
vacuity. The section is subquadrangular, much wider than high, 
the ratio of the two diameters being about 23 to 36. The periidiery 
is broad and flattened, and “ has two very obscure longitudinal 
ridges, with a distinctly flattened space between.” The sides are 
strongly convex and slope abruptly inwards. The septa are G lines 
distant from each other on the sides of the shell, where the ventro- 
dorsal diameter of the whorl is 21 lines ; their sutures form a very 
shallow sinus on the periphery. The siphuucle is situated close to 
the margin of the periphery. Along each ventro-lateral margin 
there is a row of strong prominent nodes, which are exposed upon 
the inner whorls as well as upon the last ; thirteen may be counted 
on the penultimate whorl. 
“ The surface is without longitudinal lines, but the striae of growth 
are moderately distinct, especially on the broad flattened outer side, 
where they make a deep backward curve in crossing, so as to indi- 
cate the presence of a very deep sinus in the lip on that side of the 
aperture of the shell. . . . The substance of the shell is thin and 
scarcely mineralized, though it retains no pearly lustre.” 
Remarlcs. The passages between inverted commas in the foregoing 
description are taken from Meek and Worthen’s account of the 
species. The British Museum specimen being, however, much more 
perfect than theirs, which was only about half of a volution, I have 
been enabled to add many particulars of characters which were 
wanting in the type specimen. (See p. 143, fig. 23.) 
This species is closely allied to Nautilus {Temnocheilus) Wiusloivi, 
Meek amd Worthen (Proc. Acad. Nat. Sci. Philadelphia, 1870, p. 50), 
but the latter has its volutions proportionally narrower, measured at 
right angles to the plane of the shell. The nodes also are round, 
instead of being distinctly compressed, as in the present species 
These differences may, however, be only of varietal importance. 
Temnocheilus latus has already been compared with T. tuherm- 
latus, J. Sowerby, under the description of the latter. 
Nautilus aeanthicus, Tzwetaev\ of the Tipper Carboniferous rocks 
^ “ Cephalopodes de la Section Sup4rieure du Calcaire Carbonifere cle la 
Eu.ssie Centrale,” Mem. du Com. Geol. (St. Petersburg), 1888, vol. v. no. 3, 
pp. G and 45, pi. i. ff. 1, 2. 
