44 
NATJTILOTDEA. 
Sp. Char. Section circular. Kate of increase 1 in 11. Septa 
regular and horizontal; their distance varies with the diameter, 
which it is sometimes equal to, and sometimes exceeds. The body- 
chamber is quite unknown. The siphuncle is central. The surface 
is ornamented with very fine transverse stri£e. 
Remarhs. Barrande applies the name 0. acuarium with doubt to 
some fragments resembling Count Munster’s species, which was 
itself founded upon incomplete specimens ; hence the uncertainty 
that prevails regarding this form. 
Horizon. Etage E ( = Salopian). 
Locality. Lochkow, Bohemia. 
Eairly well represented in the Collection. 
Orthoceras senile, Barrande. 
1866. Orthoceras senile, Barrande, Syst. Sil. de la Boheme, vol. ii. 
Texte iii. 1874 (jamier), p. 589, pi. ccxxiii. IF. 11-15, pi. cccxxxiv. 
fi. 1, 2, & 7-15. 
Sj). Char. Section circular ; the occurrence of one or two indi- 
viduals in which it is elliptical being deemed by M. Barrande to be 
accidental. Kate of increase about 1 in 7. Septa averaging about 
1 the diameter in their distance from each other. Length of the 
body-chamber varying between 1 ^ and 2| times the diameter of its 
base ; that is, equalling nearly J the total length of the shell. Si- 
phuncle eccentric, placed about midway between the centre and the 
circumference. Surface with very distinct, irregular, transverse 
riblets, covered with very fine, longitudinal striae, which can only 
be distinguished with the aid of a lens ; these pass over the riblets. 
Horizon. Etage E, bande e 2 ( = Salopian). 
Localities. Kosorz, Wiskocilka, Bohemia. 
Eairly well represented. 
Var. Hoernesi, Barrande. 
1866. Orthoceras Hoernesi, Barrande, Syst. Sil. de la Boheme, vol. ii. 
Texte iii. 1874, p. 507, pi. ccxiii. tf. 4-6, pi. cccxxxiii. ff. 1-16. 
Remarhs. This form does not differ from 0. senile, except in the 
absence of the fine longitudinal striae, and I have therefore reduced 
it to varietal rank, as I do not consider such a character of sufficient 
importance for specific distinction. 
Horizon. Etage E, bande e,2 (= Salopian). 
Localities. Lochkow, Kosorz, Bohemia. 
Well represented in the Collection, 
