KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 23. N:o |2. 35 
also be quite contrary to Ascoceras, in case, what is not certain, the convex side of the 
shell is the ventral side and the concave side the dorsal one as assumed in Ascoceras. 
In Choanoceras the lacunose:part of the septa is placed against the convex side, in Asco- 
ceras again near the concave side. 
If I am right to interprete, as has been done below, the smaller specimens with 
four complete septa as younger stages in which the lacunose septa had not yet been de- 
veloped, then there is the great dissimilarity between this genus and Ascoceras, that in the 
former the initial stages already foreshadow the appearance of the latest, through the 
great similarity of the septa, whilst in Ascoceras there is a long continuation of a regu- 
lar Nautiloid growth or structure before the Ascoceras stage sets in. In Choanoceras the 
truncation seems to have been executed regularly before the shell had attained its final 
shape. In the siphunele both of Ascoceras and Choanoceras the nummuloid elements are 
prevailing, but are more developed in Choanoceras, which also has the necks of the 
septa larger. 
Besides this genus there is another Cephalopodan shell of unknown affinities (Pl. 
VIT figs. 18—20) with much pointed and funnel like septa, but regularly placed on the 
median axis of the straight shell, so that the siphuncle coincides exactly with that axis. 
As seen by the figures the neck of the septa is uncommonly long and continues down 
till it meets the bottom of the next septum, thus forming, as it seems, the entire si- 
phuncle. It thus cannot be shown to belong to this group, having only the similarity of 
the extraordinary pointed septa. 
Sp. Choanoceras mutabile n. 
PIE VIL fos: 6—19, pl> VIL figs: 1—17. 
Distribution: In the uppermost limestone strata of Samsugn and Klints in Othem, 
from Stor-Wede in Follingbo and from the shore of Boge, probably in a piece of lime- 
stone detached from the overlying limestone rock. 
This remarkable fossil occurs in sets of two different forms, distinguished by their 
interior structure, but exteriorly quite similar. The shell resembles a faintly curved Ortho- 
ceratite, cylindrical and regularly circular in a transverse section. At the inferior, trun- 
cated end it is pointed into an oblique cylinder, bordered superiorly by an oblique edge. 
It is very difficult to decide which side is to be regarded as the ventral one and which 
as the dorsal, as contrary to Ascoceras the septa are smallest near the convex side. 
The surface is commonly glossy through weathering, but in some spots there is still 
the original ornamentation left (Pl. VII figs. 5, 10 & 14) consisting of longitudinal, wavy 
and sometimes interrupted lines. The surface of the largest specimen (Pl. VI figs. 6, 7, 9) 
is covered by microscopically small elevated points (fig. 6 a), probably not superficial, but 
belonging to an interior stratum of the shell. On the surface there is near or immedi- 
ately above the truncature a belt where the sutures of the septa are plainly seen running 
in equidistant parallel lines (Pl. VI fig. 6—9). 
A common feature of all specimens is the large size of the body chamber. In the 
largest specimen, 9,6; centim. in length, it occupies I centim, and in the same way pro- 
