GOMPHOCERATID^. 
239 
axes being in the ratio of 4 to 3. The increase is very rapid, being 
in the ratio of 1 : 4 in a length of 30 millim. in the septate part of 
the shell. The hody-chamber is about ^ the total length of the shell 
in the adult, but it is nearly | of the same in the young. The general 
surface of the aperture makes an angle of about 20° with the plane of 
the last septum. The lobes of the larger orifice are perfectly symme- 
trical, the pair on the dorsal side being somewhat longer than the 
other pair. The median saddle is rather deep, so as considerably to 
contract the orifice. The smaller orifice forms in adult specimens an 
oval termination to the narrow channel connecting the two orifices ; it 
projects slightly beyond the ventral border. The septa are moder- 
atel}’ distant from each other ; about ^ the diameter of the shell ; 
the last two are much nearer together than the rest. The siphuncle 
is situated near the ventral border for the greater part of its length, 
but in the earlier stages of the growth of the shell it must be almost 
touching the test. The width of the siphuncle is equivalent to 
about 1 the ventro-dorsal diameter of the shell. The test is orna- 
mented with numerous irregular lines of growth, which bend down- 
wards upon the ventral border and form there a narrow sinus. The 
base of the body-chamber is beautifully creimlated in most ex- 
amples of the species. 
Remarks. A species very closely allied to the present one is 
Tetrameroceras (Pliragm.) discrepans, Barr. (pi. xlix. &c.), but it 
differs in the position of the siphuncle, which is very nearly central, 
and in the form and proportions of the lobes of the larger orifice, 
these being nearly equal in length. 
Horizon. Etage E ( = Salopian). 
Localities. Lochkow, Dlauha Hora, Bohemia. 
Bepresented in the Collection by two examples. 
Tetrameroceras vetus, Barrande, sp. 
1847. Gcmphoceras vetus, Barrande, Haidinger, Berichte fiber die 
Mittheil. von Freund, der Naturwiss. in Wien, Band iii. p. 2G9. 
1867. Phragmoceras vetus, Barrande, Syst. Sil. de la Boheme, vol. ii. 
pt. i. p. 231, pi. liv. 
Sp. Char. Shell nearly straight, the dorsal side being, as usual, 
the more convex. The transverse section is oval, the two axes 
being in the ratio of 5 to 4. The rate of increase amounts to about 
2 in 5, though in some individuals it is still more rapid. The body- 
chamber occupies about 5 of the total length of the shell, and its 
capacity is nearly equal to that of the septate part. The plane of 
the aperture forms an angle of about 40° with that of the last 
