16 G. LINDSTRÖM, THE ASCOCERATIDA AND THE LITUITIDAE. 
no exterior sculpture nor is the youngest or uppermost air chamber larger than the others. 
There has never been formed a living chamber, as it was no need of it. An increase in 
the volume of the body must also have occurred in such genera as Gomphoceras and 
Poterioceras, of which the later bears no slight resemblance to Ascoceras. When the shell 
had been completed the mollusc has drawn higher up in it and commenced the secre- 
tion of the sigmoid septa. Near the ventral side the place of the animal has not been 
much changed, at the dorsal, again, it moved more and more upwards. 
The genus Ascoceras may now shortly be characterized as follows: 
Shell, at first Nautiloid, curved as a Cyrtoceras, with concave, oblique septa, ir- 
regularly distantiated, with tubular, ventral siphuncle. In its adult stage it changes into 
a pyriform, elongated, laterally compressed shell with a cylindrical, necklike and simple 
aperture. The septa of this shell are sigmoidally curved high up against the dorsal side 
and low and concave near the ventral one, incomplete (from the second inclusive) in their 
central area. The siphuncele is ventral, oblique, of broad, nummuloid elements. 
To show the geological distribution of the species of this genus, as well as of the 
other two genera the subjoined table is given. 
Stratigraphical Distribution of the Swedish Species of Ascoceratidee. 
| | Sit r ata! 
| Her k Tv I TON 
| a. RR Er EA | e KEN 9. | h. 
| | 
Ascoceras BARR. | | | 
| 
I ja A. cochleatum | TSE SS SINE EROSION EOS Na Sao TN | Xx rr a | fan pa re? JT 
| , NÅR Rn mn pr no Aa SNR RE SAN AE = | =—" 1] — = | — | — [Nee x 
ds CAS UOLUNIL Mlpoae no aboard AA RES TEN TERESE NNE SURT — ll «ll —-!I—-1]— va — I 
GA INDUS Ina. tre TION AT SAR URISRSEENA SETT Segt (== | 21 | Faa 
Inet AOrptipafblgoo stolar seal Mb Inorne ad 2) FINS IG + ÖllRSK9N0 
da Atsreticulstämiin=rssandotosd ETTA kt Sr föl fe dem frekaSUlN 
Bon As, Bobb en BARR såna oda a RR | EB =S Tr 
7 (NR VAR Tatra ert ads (6 1 NES SERA RS FUN FSE ET LO bag NA sd — |] — I + 
ARN Arr rR I Sri Vr ge SA rr GA SE SEN SEDER an DEN AT — | | - = =] — |] — + 
| | | 
|. SJ.” COLIGNG IIS ekon asect oltp ie cR one v a ot PE ETTER SEIN SESEES Mr fat a KR RK 
1:10! "AK FIngéha fe. rn. EYE EET JESTIUNUNT ONE EH =I-1l—-1l—-/|—-!I1—- ör 
I OG tönt Ju ==) = 
124 AN dedipiendidftses] is tsåtooskoor a dato bt ernner talen läafaoli — Ib) a 
Ila, Hin: AE BR ARE | -I1— I] —-ha 
ESR VRT dd a Ub TRE SRS RR ENSE SE SKO RE RE Ta RN Pr Keg Ag FR ee 
12358 AR NER ft 0 SEA BERER SETS NE ER BRA a ek a i | | | NR 
Glossoceras BARR. 
| GI. grace BARR. VÄ. CUL(A ,«...-=--emssvor Fp Era Br I | - | 1] —" TON 
| | 
| Choanoceras un. | | | 
I Ch. INUSRDILO "Ir esurkorelecbenans see op ease kh Sad Ear = -=I—I I-II = + 
