CEPHALOPODA. 
411 
Nautilus lie at us, var. juvenis, n. var. 
PLATE LVI, PIGS. 5, 6. 
Nautilus liratus, Hall (in part). Illustrations of Devonian Fossils: Cephalopoda, pi. 57, figs. 5, 6. 1876. 
* 
Shell subovoid, discoid. Transverse section elliptical. The ventro-dorsal 
diameter about three-fifths as great as the transverse diameter. A part of 
the difference being probably due to moderate compression. 
Volutions rapidly expanding from near the base of the great cham¬ 
ber, which is subovoid, with unequal diameters. Number of volutions 
unknown. 
Chamber of habitation deep and wide, having a length, on the convex side, 
of fifty-five mm., with an equal transverse diameter at the aperture, and a 
ventro-dorsal diameter of twenty-eight mm. Aperture transverse to the 
direction of the tube, elliptical in outline. Ventral side entire, without sinus. 
Air-chambers not satisfactorily determined: there are about four attached 
to the base of the grand chamber, which are partially crushed and the form 
distorted. 
Septa direct, moderately concave. Suture lines not satisfactorily observed. 
Siphuncle obscure, apparently small and subcentral. 
Test thin, imperfectly preserved on the specimen. Surface, in the partially 
preserved shell, marked on the -concave and lateral faces by slender, sharp, 
cariniform ridges, of which there are fourteen or fifteen on each side, 
becoming gradually subdued and obsolete on the convex or ventral side. 
Ventral side marked by about twenty subdued, rounded, longitudinal striae, 
which are arranged at subequal distances on each side of a wider median 
space. Entire surface marked by fine, even, transverse, thread-like striae, 
which traverse the flat or concave interspaces, and arch over the ridges, 
producing a crenulate aspect. On the ventral side these transverse striae 
are more conspicuous than the longitudinal striae, which do not perceptibly 
interrupt their course. The surface is farther marked by low, rounded and 
inconspicuous, transverse undulations, of which about eleven may be counted 
on the grand chamber. No sinus has been observed in the margin of the 
