OKTHOCERVTID^. 
49 
Orthoceras tenuiannulatum, 
ISol. Cychceras tenuiarmulatum, Ann. & Nat. Hist, 
ser. 2, Yol. vii. p. 4o. 
18-52. Ci/cloceras tenuiannulatum, M‘Coy, British Pal. Foss. fasc. ii* 
p. 320, pi. iL.f. 31. 
18-52. Cycloceras ibex, M‘Coy, ibid. p. 319 (pars). 
18-52. Orthoceras ibex, Salter, ibid. Appendix A, p. vii. {Not of Sowerby.) 
18-54. Orthoceras vertebrate, Morris, Cat. British Foss. p. 312. (Ab^ 
of Hall.) 
180-5. Orthoceras tenuiannulatum, Hasvrell, On the Siliman Formation 
of the Pentland Hills, p. 25, pi. i. f. 3. 
1873. Orthoceras tenuiannulatum, Salter, Cat. Cambr. and Sil. Foss, 
p. 17-3. 
1873. Orthoceras ibex, Salter, ibid. p. 186. 
1832. Orthoceras tenuiannulatum, Blake, British Foss. Ceph. pt. i. p. 98, 
pi. v. if. 9, 9 a. 
Sp. Char. Section not known, owing to compression. Bate of 
increase variable, about 1 in 14. Septa, siphimcle, and body- 
chamber unknown. Surface ornaments consisting of very clearly 
separated rounded ribs, the interspaces wider than the latter. The 
ribs are slightly oblique, and are distant ^ to the (flattened) 
diameter. Fine longitudinal lines, about 20 in the space of 1 line, 
cross the ribs, and a few transverse lines are seen on the summits 
of the ribs. The longitudinal and transverse lines in small (young ?) 
individuals sometimes become closely cancellated. 
Horizon. Wenlock Shales (Salopian). 
Localities. Dudley, Worcestershire ; Byton Cross, Herefordshire ; 
near Presteign, Kadnorshire. 
Fairly well represented in the Collection. 
Orthoceras Duponti, Barrande. 
1868. Orthoceras Dnponti, Barrande, Syst. Sil. de la Boheme, vol. ii. 
Texte, iii, 1874 (janvier), p. 324, pi. ccxii. ff. o-13, ? pi. ccxiv. 
ff. 9, 10, pi. cclxxxv., pi. cccxxiv. ff. 7-10, pi. cccxciv. ff. 1-4. 
1873. Orthoceras subannulare, Salter, Cat. Cambr. and Sil. Foss. p. 98. 
1882. Orthoceras Duponti, Blake, British Foss. Ceph. pt. i. p. 92, pi. v, 
ff . 1, 1 a, 2, 2 a. 
Sp. Char. Shell always straight. Section circular. Bate of 
increase 1 in 10. Septa direct, very variable in their distance ; 
from I to 1 the diameter. Body-chamber four times the length of 
its basal diameter. Siphuncle eccentric ; about |- across the dia- 
meter ; its elements slightly inflated. Ornaments changing with 
growth. In the apical portion of the shell there are annulations, 
slightly oblique and close-set, occupying a space greater than the 
spaces separating them. At a certain period in the growth of the 
E 
