NAniLID^. 
53 
siphuncle is quite internal, almost touching the inner border. Septa 
rather distant, in whorls 5 lines deep, nearly 2 lines apart, not very 
convex, moderately arched backwards on the sides, and straight, or 
only gently curved across the back. 
“ This species puts one in mind greatly of the Z. {TrocJiolites) am- 
moniits of Conrad, a Lower Silurian species from Xorth America, 
and belongs to the same division of the genus. It differs in being 
much less compressed from back to front.’’ (Salter.) 
Remarhs. The “Cephalopoda” [of Xiti] says Salter (Zoc. p.l2), 
“ remind us, by their general characters, of those of other Silurian 
regions. This may certainly be said of the species of the genus 
Orthoctras. The 0. Kemas is exactly like a common Ludlow Rock 
fossil. The species of Liiuites can scarcely be otherwise than from 
the same Silurian group ” 
Horizon. Silurian? 
Lineality. Chorhoti Pass (18,200 feet), Himalaya Mountains. 
Genus GYROCERAS, de Koninck k 
\_Gyroceratites, von Meyer, 1831 • ; Spirula^ Goldfuss, 1832 Hortohis, 
Steininger, 1834* *; SpiruUtes, Quenstedt, 1836 ’; Broun, 1837®; 
Cyrtoceras, Phillips, 1841 ; CyHoceratites, d’Archiac and de ^*e^neuil, 
1842**; Comdaria, Fischer, 1848®; Xautiloceras, Apheeras, d'Orbigny, 
1840^° ; llalloceras, Kophinoceras (pars), Apsidocerae ?, Triholoceras (pars), 
Hyatt, 1883**.] 
Spec. Char. Shell forming a single whorl, or several whorls, coiled 
upon the same plane, just touching, or completely out of contact. 
Transverse section subcircular, transversely elliptical or subtriangular. 
Body-chamber of moderate size, generally occupying about one-third 
of the last whorl, though this proportion is exceeded in some Carbo- 
niferous species. Aperture simple, emarginate on the ventral or 
' Descrip, des Anim. Foss, du Terr. Carb. de la Belgique, 1844, p. 530. 
2 Nova Acta Acad. Leop.-Carol. vol.xv. pt. ii. p. 73. 
^ In von Dechen’s Handb. der Geognosie von H. de la Beche, p. 536. 
* Mem. de la Soc. Geol. de France, vol. i. pt.ii. p. 370. 
® De notis Nautilearum primariis, p. 24. 
® Lethsea Geognostica, Band i. p. 102. 
■* Pal. Foss, of Cornwall, Devon, and West Somerset, p. 115. 
® Trans. Geol. Soc. ser. 2, vol. vi. p. 340. 
® Bull. Soc. Imp. des Nat. de Moscou, vol. xxl. p, 6. 
*° Prodr. de Paleont. Stratigr. vol. i. p. 112. 
** Proc. Boston Soc. Nat. Hist. vol. xxii. pp. 284-294. 
