14 G. LINDSTRÖM, THE ASCOCERATIDZE AND THE LITUITIDA. 
Gen. ASCOCeras8 BARRANDE. 1848. 
Syn. Cryptoceras BArRrR. 1846. Notice prel. sur le Systeéme Silur. et les Trilobites de Bohéme p. 43. 
>  Ascoceras BARR. 1848 in HaAIDINGER'S Berichte iber die Mittheilungen von Freunden der Naturw. in Wien 
Bd: IIT, ps 268: 
Aphragmites BARR. 1865. Syst. Sil. de Bohéme vol. II, 1fre Série, pl. 1 å 107, fourth page of »Distri. 
bution». 
This remarkable genus is during a long period of its life Nautiloid as to the struc- 
ture of its shell and at last changes into that shape, which for so long a time has been 
alone known as the Ascoceras. There are thus two stages to be taken in consideration 
separately, in a description, viz. 1) the Nautiloid, and 2) the Ascoceras proper. 
1. The Nautiloid. I have called this stage so, because it corresponds with the 
common type of the suborder of the Nautiloidea. It cannot properly be called an Orthocera- 
tite stage as the shell is not straight, but curved and thus rather a Cyrtoceras, having 
also the siphunele formed in accordance with that genus. If it ever was quite entire and 
intact, before attaining its last stage, the shell has been bent in a large arch, pl. VI fig. 3, but 
it is evident that it broke off and was decollated several times during its growth. In some, 
(Asc. fistula) pl. VI, f. 2, the Nautiloid was more straight, though somewhat twisted. 
The thin shell which only slowly widened, is generally transversally striated or annular 
with small modifications in the different species. The interior structure is highly uniform 
in all, with oblique watch glass like septa, higher on the dorsal side than on the ventral, 
placed at much irregular distances from each other, sometimes close, sometimes widely 
apart, the distance increasing with the augmenting width of the shell. The siphunele is 
always placed near the ventral side and consists of tubular, narrow elements, enclosed in 
a calcareous sheath of their own and connected with the funnel of the downwards curved 
septal aperture. In some there is a tube on the upper surface of the septum, which en- 
closes the basis of each siphonal element. 
2. The Åscoceras proper. "The shell, often pyriform or flaskshaped, consists of two 
different portions, the lower or the larger, usually wider portion, containing the septa and 
its more narrow necklike continuation, ending with the round aperture. 'The shell is almost 
always flattened from two opposite sides, in the lower or essential portion with an ovate 
section and cylindrical in the neck with circular section. There are two different sorts 
of septa: 1) Regular, Nautiloid septa and 2) Sigmoid, Ascocerate septa proper. The first 
septum, which in fact may be regarded as the last Nautiloid septum and forms the bot- 
tom of the shell, is strengthened from within by organic deposits of calcareous matter. 
It is in a distinct group of species followed by a second septum of regular shape, but in 
the plurality of species the abnorm sigmoid septa follow immediately on the first. The 
number of the sigmoid septa varies from three to seven, but is very constant in one and 
the same species. A fragmentary specimen of an unknown species has indications of no 
less than twelve septa (Pl. IV fig. 38, 39). The septa are continuous from the ventral to 
the dorsal side, as may be seen in so many nuclei, where the sutures continue uninter- 
ruptedly across the shell (PI. II f, 16, pl. IV f. 45 ete.). But in the interior of the shell 
