14 
NATJTILOIDEA. 
On the opposite side is a groove between two prominent ridges; 
the whole forming the ventral keel. The body-chamber, including 
the straight piece, occupies nearly half of the external volution. 
The aperture is unknown, but there is reason to suppose that it 
resembled that of OpMdioceras simplex. The septa are distant about 
^ a line measuring from suture to suture, upon the sides of the shell, 
and a little more than this upon the periphery. The siphuncle is 
situated at a little distance from the ventral or convex border of the 
shell, and is composed of small cylindrical segments, similar to those 
of Opliidioceras simplex. The surface of the shell and of the cast is 
ornamented with prominent nearly transverse annulations, each 
corresponding with a septal chamber, the direction of the former not 
however, coinciding perfectly with the latter. The finer ornaments 
consist of a network of minute raised lines, which are more distinct 
in the spaces between the annulations than upon them. The longi- 
tudinal lines of this network appear to become obsolete upon the last 
whorl, so that they may belong only to the younger stages of the 
growth of the shell, in which case their specific importance would be 
greatly reduced. 
Remarics. This species is very closely allied to Opliidioceras sim- 
plex, from which it is distinguished only by its ornaments. 
Horizon. Etage E, bande e2 ( = Salopian). 
Locality. Hinter Kopanina, Dlauha Hora, Butowitz, Bohemia. 
Fairly well represented in the Collection. 
Family TROCHOCERATIDtE. 
Genus TROCHOCERAS, Barrandek 
[Litmtes, J. de 0. Sower by, 1839^; Lituites, Hall, 1847^; Lituites, 
]\BCoy, 1852 4 5 Hortolus, MEoy, 1852^; Lituites, Morris, 1854“; 
’ Haidinger’s Berichte iiber die Mittheil. von Freund, der Naturwiss. in Wien, 
Band iii. September 1847, p. 266 ; also Syst. Sil. de la Boheme, vol. ii. pt. i. 
p. 74. 
2 Murchison’s Sil. Syst. pt. ii. p. 643 (Z. cornu-anetis). 
^ Pal. New York, vol. i. p. 52, pi. xiii. ff. 1 a, 1 5 (excl. ff.T, 2, 3 of same plate, 
and pi. xiii. (bis) f. 1). 
4 British Pal. Foss. fasc. ii. p. 323. 
Ibid. p. 324 {H. giganteus). 
“ Cat. British Foss. 2nd ed. p. 305. 
