Prof. G. Lindstrém—On Ascoceras of Barrande. 533 
ment of the Swedish State Museum, the number of species of Cepha- 
lopoda from the different strata of Gotland can hardly fall short of 
200, most of them in a very perfect state of preservation, some even 
retaining the surface ornamentation and colour. Amongst them the 
genus Ascoceras (including Glossoceras), with its nine species, is the 
most remarkable. As the Museum has succeeded in obtaining 
specimens showing its morphology more completely than has 
hitherto been known, a few remarks on it may be made in advance 
of a monograph now in preparation. 
The annexed figure represents 
a longitudinal section of a speci- 
men from the uppermost lme- 
.stone. It is imperfect on the 
ventral side, but the characteristic 
septa along the dorsal side show 
distinctly that it is an Ascoceras. 
We see here two essentially 
different parts of the shell: firsé, 
a lower part in which two entire 
air-chambers and a portion of a third 
yet remain, which are fashioned, 
after the common Nautilidean type. 
The second or upper portion in 
immediate continuation and con- 
nexion with the former, is the 
Ascoceras properly so called. The 
entire shell must have been arcu- 
ate or gently curved, like some 
forms of Cyrtoceras, but it is doubt- 
ful if complete specimens ever 
existed, since several examples 
clearly show that the older parts  Aseoceras sp., U. Ludlow, Isle of 
of the shell were, at certain inter- Gotland. 
vals, regularly cast off or decollated. The truncated end appears in 
all cases to have been strengthened from within by fresh linings 
of shelly material, and the animal continued to secrete its shell till 
the <Ascoceras portion was formed. When this was finished, at 
least exteriorly, the older portions of the shell were, as a rule, 
decollated, and hence the Ascoceras usually occurs by itself without 
the early, or Nautilus stage, and specimens like that figured are 
extremely rare, and in fact, only a few examples from Gotland have 
as yet been discovered. 
This strange and abnormal Cephalopod thus went through two 
sharply-defined stages during its growth, the first, probably of 
longest duration, the Nautilus, and the second, the Ascoceras stage. 
Broken-off stumps of the former stage have been found, which can 
be matched to five of the nine Gotland species of Ascoceras. They 
all show the characteristic peculiarities of a narrow thin shell, very 
gradually increasing in width, oval or elliptical in transverse section, 
and ornamented by oblique, transverse strie. The body-chamber 
