99 
Discites (Phacoceras) oxystomus, Phillips, sp. 
18o6. Xautilus oxystomus, Phillips, Geol. of Yorkshire, pt. ii. p. 233, 
pi, xxii. IF. 35, 36. (Yb^ of II. Trautscholcl \) 
1843. Xautilus oxystomus, de Koninck, Descrip, des Anim. Foss, dii 
Terr. Garb, de la Belgique, p. 544, pi. xlix. ft*. 3, «, h. 
1844. Xautilus (^Discites) oxystomus, M‘Coy, Synop. of the Carbouiferous 
Foss. Ireland, p. 18. 
1847. Xautilus oxystomus, d'Orbigny, Paleont. UniTerselle, vol. i. pi. cv. 
ft*. 3, 4. 
1849. Xautilus oxystomus, d'Orbigny, Prodr. de Paleont. Stratigr. vol. i. 
p. 111. 
1854. Xautilus oxystomus, Morris, Cat. British F'oss. p. 308. 
1855. Xautilus oxystomus, M‘Coy, British Pal. Foss. fasc. iii. p. 560. 
1860. Discites oxystomus, Griffith, Journ. Geol. Soc. Dublin, vol. ix. 
p. 33. 
1878. Xautilus oxystomus, de Koninck, Faune du Calcaire Carbonifere 
de la Belgique (Annales du Mils. Roy. d’Hist. Nat. de Belgique, 
tom. ii.), pt. i. p. 123, pi. xvii. IF. 3 a, 3 h. 
1883. Phacoceras oxystomum, Hyatt, Genera of Fossil Cephalopods,’ 
Proc. Boston Soc. Nat. Hist. vol. xxii. p. 293. 
/ 87 J. Char. “ Lenticular, very much compressed laterally ; greatest 
thickjiess at the edge of the small shallow umbilicus, from whence 
the sides slope, almost flatly, to the thin, very acutely carinated 
periphery ; whorls about four, their edges distinctly visible in the 
umbilicus; the mouth very elongate, lanceolate, embracing three- 
fourths of the sides of the penultimate whorl. Surface of inner 
whorl spirally sulcated, of the outer turns smooth, or with extremely 
fine, obsolete transverse lines of growth, having a very strong forward 
wave in the middle, and a small, slightly marked one at the sloping 
edge of the umbilicus. Internal casts show the septa strongly arch- 
ing forwards from the umbilicus to a flat, solid band, about two or 
three lines wide, produced by the internal cavity not quite reaching 
the edge ; the last chamber occupies rather less than half the last 
whorl, and is marked by a narrow, deep sulcus, a little on the inner 
side of the middle, produced apparently by a corresponding ridge 
on the interior of the shell, of which there no trace on the out- 
side 
“ I have not been able to observe the siphuncle in this species, 
but according to de Koninck it is very small and nearly central, a 
little outside of the middle. The inner whorl is scarcely embraced 
by the succeeding one, is not compressed, and has a broad, convex 
^ Nouveaux Memoires de la Soc. Imp. des Nat. de Moscou, tom. xiii. p, 304, 
pi. XXX. f. 7. 
