CTRTOCEEATID^. 
293 
diameters in an adult specimen is as 6 : 5 The rate of increase is 
about 1 in 2, measured in the septate part of the shell. The body- 
chamber varies in its relative length, but it may be taken at about 
|- of the total length of the fossil ; its capacity is nearly equal to 
that of the whole of the septate part of the shell ; the base is some- 
times crenulated. The aperture is for the most part parallel to the 
plane of the last septum, in rare cases it is inclined towards the 
convex side. The distance between the septa varies very consi- 
derably in different individuals : thus, iu a short and wide form it 
is ^ of the diameter of the shell, in a long individual it is i of the 
same near the body-chamber. The siphuncle is situated close to 
the concave border ; its elements are on the whole elongated and 
cylindrical ; in some specimens, however, they have a tendency to 
become nummuloidal between the uppermost septa. The surface 
of the test is ornamented with irregular lines of growth, which have a 
lamellose appearance in certain individuals ; they form a sinus both 
on the convex and the concave borders of the shell. Longitudinal 
lines are seen upon the cast of the body-chamber. 
RemarTcs. This species is distinguished from all others of the same 
group by its large size, by its straightness, and by the form of its 
siphuncle. 
Horizon. Etage E ( = Salopian). 
Localities. Kosofz, Lochkow, Hinter-Kopanina, Bohemia. 
Well represented in the Collection. 
Cyrtoceras (Meloceras) hybrida, Barrande, sp. 
1848. Cyrtoceras hybrida, Barrande, Haidinger, Berichte iiber die 
Mittheil. von Freund, der Naturwiss. in Wien, Band iv. p. 208. 
1852. Cyrtoceras hybrida, Giebel, Fauna der Yorwelt, Band hi. Abth. i. 
p. 209. 
1867. Cyrtoceras hybrida, BaiTande, Syst. Sil. de la Boheme, vol. ii. 
pt. i. p. 662, pi. clxxvii. ff. 1-11. 
Sp. Char. Shell moderately curved; upon a chord of 70 millim., 
subtending the concave side, the highest perpendicular is 5 millim. 
The transverse section is nearly circular. The rate of increase is 
about 1 in 2 in the septate part of the shell. The body-chamber 
occupies nearly ^ of the total length, and its capacity is nearly that 
of the whole of the septate part. The distance between the septa 
increases regularly until it attains to i of the diameter of the shell. 
There are about 40 septa in the entire shell. The siphuncle is 
situated close to the concave border, without coming in contact with 
the test ; its elements are cylindrical, becoming somewhat cordiform 
in the upper part of the shell. The surface of the test is ornamented 
