OETHOCERATlDiE. 
23 
1870. Orthoceras Vibrayei, Barrande, Distrib. des C^ph. dans les Con- 
trees Siluriennes, p. oO (Extr. du S jst. Sil. de la Bobeme, vol. ii. 
4me ser.). 
Sjp. Char. Section circular. Bate of tapering about 1 in 14. 
Septa distant rather less than | the diameter. Body-chamber 
unknown. Siphuncle nearly central. Test almost smooth. 
RemarTcs, The Collection contains only a fragment of the septate 
portion of the shell showing the nearly central siphuncle. 
Horizon. Calcaires ampeliteux ( = Third Eauna of Barrande). 
Localitij. iS'ormaudy, France. 
Orthoceras tritonum, Barrande. 
1868. Orthoceras Tritonum, Barrande, Syst. Sil. de la Boheme, vol. ii. 
Texte iii, 1874 (janvier), p. 661, pi. eecxlv. ff. 13-22, pi, cccxlvi. 
ff. 19-21. 
Sp. Char. Section elliptical. Bate of increase very slow, about 
1 in 16. Septa very numerous, undulating, about ^ the diameter. 
Body-chamber var3ung in length from twice to three times the 
basal diameter, but it is sometimes reduced to less than 1^ times 
that diameter. Siphuncle a little eccentric. Surface smooth, or 
showing only some feeble lines of growth. 
Horizon. Etage E, bande « 2 ( = Salopian). 
Localities. AViskocilka, Kosofz, Bohemia. 
AVell represented in the Collection. 
Orthoceras truncatum, Barrande. 
1860. Orthoceras truncatuni., Barrande, Bull. Soc. Geol. France, tom. 
xvii. 2® ser. p. 573, pi. ix. ff. 1-20. 
1868. Orthoceras truncatum, Barrande, Sj'st. Sil. de la Boheme, vol. ii. 
Texte iii. 1874 (janvier), p, 656, pi. cccxli. (excl. tf. 3-7), 
pi. cccxliii. (excl. f. 14), 
1882. Orthoceras truncatum, Blake, British Foss. Geph. pt. i, p. 161, 
pi. xiv. tf. 8, 8 a. 
Sp. Char. Section elliptical, the diameters in the ratio of 5:4; 
individual variations excepted. The rate of increase is vury slow, 
the body-chamber decreasing in size towards the aperture, which is 
oblique and undulating. The septa are nearly direct, and distant 
about 1- the diameter ; they are very strongly convex. The suc- 
cessive chambers drop off, the truncated extremity thus caused 
being protected by a calcareous deposit. The siphuncle is small 
and a little eccentric, as a rule, though in some examples it appears 
to be central. The test is almost smooth, but is marked with 
feeble striae, which have a tendency to direct imbrication. 
