OETHOCERATID^. 
43 
nearly circular, but most frequently elliptical, with the diameters in 
the ratio of 11 : 9. Eate of increase rapid, about 1 in o. Septa 
rather distant, reaching a maximum distance of 4 the diameter. 
Body-chamber variable in length in different individuals, from 
twice to three times the diameter of the base. Siphuncle slightly 
eccentric, about f across the longer diameter. Surface with slightly 
oblique transverse strise, rather wide apart. 
BemarJcs. In a note at the head of the description of this species 
given by 41. Barrande (loc. that author observes that he had 
already communicated specimens of this Orthoceras, under the 
name of 0. hians, and such was the name borne by the specimens 
in the National Collection. It appears, however, that this name 
was preoccupied by Dr. E. Eichter de Saalfeld, in 1866, for a 
Devonian species, and therefore a new one was chosen. 
Horizon. Etage E, bande e 1 (=Valeutian, or Salopian?). 
Locality. Butowitz, Bohemia. 
Fairly weE represented in the Collection. 
Orthoceras mutabile, Barrande. 
1870. Orthoceras midahile, Barrande, Syst. SD. de la Boheme, vol. ii. 
Texte iii. (janvier), p. 278, pi. ccclxxviii. ff. 4-12. 
Sp. Char. Section circular. Eate of increase 1 in 11. Septa 
very wide apart, exceeding | of the diameter of the shell in their 
separation from each other. Body-chamber of very great length. 
In a specimen figured by 41. Barrande, which is incomplete towards 
the aperture, it equals in length more than 11 times the diameter 
of its base. The siphuncle is central. Surface ornamented with 
very fine transverse striae, placed at regular distances apart ; these 
are crossed by faint longitudinal striae, which can with difficulty be 
seen, except when the light is upon them. 
Horizon. Etage E ? ( = Salopian). 
Locality. Bohemia. 
Only one imperfect specimen. 
Orthoceras acuarium ?, 4IUnster. 
1840. Orthoceratites acnariuSy 4Iiinster, Beitrage zur Petrefactenkunde, 
Heft iii. p. 95, Taf. xvii. ff. 5, a-d. 
? 1855. Orthoceras acuarium^ G. & F. Sandberger, Die Verstein. Nassau, 
Abth. i. p. 175, Taf. xx. f. 8. 
1870. Orthoceras acuarium ?, Barrande, Syst. Sil. de la Boheme, vol. ii. 
Texte iii. 1874 (janvier), p. 474, pi. ccccvii. ff. 30, 31. 
1876. OHhoceras acuarium, Tromelin & Lebesconte, Assoc. Fran?, 
pour I’avancement des Sciences, 4me Sess. (Nantes), Tabl. B. No. 32. 
