GOMPHOCEKATID^. 
219 
centre ; its elements appear to be nnmmuloidal or flattened. The 
surface of the shell is ornamented with prominent transverse plica- 
tions or rings, which are only developed in the upper two thirds of 
the shell ; three of them are much stronger and more prominent 
than the rest ; these may be situated either at the base of the body- 
chamber, or near to it in the septate portion of the shell. The 
whole of the test, including the plications, is covered with fine lines 
which run parallel with the coarser ornaments. It should be ob- 
served that in this species, contrary to the general rule, the sinus of 
the ornaments is situated on the side farthest from the siphuncle. 
RemarTcs. The three large plications, the large size of the prin- 
cipal orifice of the aperture, and the j)osition of the siphuncle are 
the characters which distinguish this species. M. Barrande observes 
that G. Agassizi is a rare species. 
Horizoyi. Etage E ( = Salopian). 
Locality. Dvoretz, Bohemia. 
Kepresented in the Collection by a few imperfect examples. 
Gomphoceras amphora^ Barrande. 
1847. Gomjplioceras amphora, Barrande, Haidinger, Berichte fiber die 
Mittheil. von Freund, d. Katurwiss. in Wien, Band iii. p. 269. 
1867. Gomphoceras amphora, Barrande, Syst. Sil. de la Boheme, vol. ii. 
pt. i. p. 272, pi. Ixxviii. tf. 10-15, pi. civ. ff. 15-17. 
Char. This species is distinguished by the inflated form of 
the body-chamber. The outline of the ventral side is strongly con- 
vex, while that of the dorsal is only very slightly so. The trans- 
verse section is nearly circular, though there is a slight difference 
between the two diameters in some specimens, the ventro-dorsal 
being in such cases in the ratio of 20 : 21 to the transverse dia- 
meter. The body-chamber occupies at least ^ of the total length 
of the shell, and exceeds the septate part in bulk. The aperture is 
characterized by its great length, by reason of w^hich the larger 
orifice opens upon the dorsal aspect of the body- chamber, instead 
of upon its apex. This feature is not so strongly developed in young 
examples. The smaller orifice is united by a very narrow channel 
with the larger one, and extends nearly halfway down the ventral 
(convex) side of the body-chamber. The distance between the 
septa, near the body-chamber, amounts to about of the diameter 
of the shell ; their convexity equals 1 that diameter. The siphuncle 
is situated midway between the ventral margin and the centre ; its 
elements are nnmmuloidal, their transverse diameter is to their 
vertical as 5 : 2, their maximum width representing -i- the corre- 
