GOMPHOCEEATTD^. 
243 
convex, the ventral side is considerably inflated at the body-chamber, 
but below that it is slightly concave, indicating a distinct curvature 
in the apical portion of the shell. The transverse section is an oval, 
of which the ventro-dorsal is to the transverse diameter as 5 : 4. 
The body-chamber occupies about ^ of the total length of the shell. 
Its capacity is a little inferior to that of the chambered part. The 
general surface of the aperture makes an angle of about 40° with 
the plane of the last septum. There are three pairs of lobes in the 
larger orifice ; two of these pairs are similar to those met with in 
Tetrameroceras. The third pair, situated nearest to the dorsal 
border of the shell, seems to be formed by the bifurcation of the 
two principal lobes, and its development is found to correspond with 
that of the individual, indications of it occurring even in very young 
shells. As the third pair of lobes develop, the median saddle (fig. 38, m) 
encroaches more and more upon the orifice. The transverse diameter 
of the larger orifice is a little more than half of the corresponding 
diameter of the shell. The smaller orifice projects a little above the 
surface of the body-chamber, and in young individuals it slightly 
overhangs the ventral border. The channel connecting the two 
orifices is narrow, especially in adult shells, in which it is almost 
closed in the middle of its course. The septa are distant from each 
other about of the ventro-dorsal diameter ; they have a slightly 
undulating course, rising perceptibly upon the dorsal border. The 
siphuncle is placed at a distance equalling its own diameter from the 
ventral border ; it is composed of nummuloidal elements of which 
the height is to the width as 1 : 2. The test is ornamented with 
lines of growth, which are for the most part very fine, but at 
intervals of about one line coarser ones appear. A series of very 
faint, longitudinal, and parallel impressions are observed upon the 
cast of the body-chamber, and the base of the latter is often cren- 
ulated. 
Remarlcs. This species is distinguished from Hexameroceras 
pollens, Barrande, sp.\ by the form of the lobes in the larger orifice 
of the aperture, by its more oval section, and by the much finer 
markiugs of the test. 
Horizon. Etage E (= Salopian). 
Locality. Lochkow, Bohemia. 
Fairly well represented in the Collection. 
1 Syst. Sil. de la Boheme, vol. ii. pt. i. p. 333. 
