26 G. LINDSTRÖM, THE ASCOCERATIDAE AND THE LITUITIDZ. 
The Nautiloid stage (Pl. TIT fig:s 12—31). In one instance both stages have been 
found still in connexion and from the structure and ornamentation of the Nautiloid in this 
special case, other detached pieces found in the same stratum, can with a high degree of 
certainty be regarded as also belonging to this species, as they have the same structure 
and ornamentation. The surface in all these has transverse annulations and is near the 
Ascoceras quite even, reckoned from the third septum and upwards. The annulations are 
very close in the youngest specimens. Parallel to them there are everywhere fine stria 
(fig:s 19, 26, 30, 31) about 12 on a length of 3 millim:s and sometimes they may be 
seen to be crossed by fine longitudinal lines. 
The shell is quite cylindrical, gradually tapering to a blunt end and faintly curved 
(fig:s 22, 26), in a transverse section quite circular (fig. 16), becoming more flattened and 
elliptic near the Ascoceras stage. 
That Nautiloid specimen which is in direct connexion with the Ascoceras (fig:s 12—17) 
contains four regular septa, obliquely concave in so far, that they are high on the dorsal 
side and deepest on the ventral side, where the siphuncele is situated. Besides a wide 
neck, as common, on their inferior surface, there is around the siphuncle a peculiar struc- 
ture of a short conical tube, widest at its base and directed somewhat obliquely upwards. 
It forms, as it were, the basis of each siphonal element (f. 17 b). The varying distance 
of the septa may best be seen through the following measures: 
Distance from the first to the second septum-.........--- 13 millim. 
» + TE 200 BieGSk- AE TN 8 » 
the '30 to” the: AMN SoA oo SES SSE 14 » 
» > tDE AUD STONE TUPINGHT mors sonas o SSA RANN 22 » 
In a second specimen (fig. 20) the distances are: 
From. the” :Labsto-Thersd.. .—u sopeseet oa JES 7 3 millim. (nearly) 
> > NO dc 10: ING UC rese ost SES a LIE TNA GSE ER S » 
+” 6 730 TD Kil Et KS SN Bs VERA EAEES TURE RR REN USE 8 » 
>» the Athitorthkev ätt. (018 sat na bed 18 » 
It may in general be said that the distance increases the farther up the septa lie, 
In a small specimen (fig. 28) there are 13 septa, very irregularly disposed on a length 
of 22 millim., and above them a very long body chamber. The siphuncle is always straight, 
narrow and cylindrical and regularly situated at a little distance from the ventral side. 
Dimensions. The specimen with Ascoceras and Nautiloid in connexion. Length 1 
decim., breadth at superior margin 22 millim., lesser diam. 16 millim. At the lower 
and dorso-ventral diam. 12 millim., lesser diam. 10 millim. 
The Ascoceras stage. "The shell is elongated, compressed or flattened, of oval section, 
the neck long and cylindrical, making a third of the whole length of the shell. The aper- 
ture is circular. The ventral side is regularly arched, fig. 3, Pl. IT, the dorsal one nearly 
straight or faintly convex. The ornamentation is nearly the same as in Ascoc. bohemi- 
cum, and consists of close set transverse riblets running obliquely over the sides and cur- 
ved down on the ventral side. "These riblets are imbricated and about 15 are contained 
within a length of 5 millim:s. On the neck they are finer and have minute, longitudinal 
strie in the interspaces. In others there are also longitudinal folds or stripes giving the 
