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Volume 56, 1926
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– 192 –

Importance of Suture-lines.

The suture-lines that are represented in Plates 1925 have been drawn with great care, and are thought to be nearly exact, though the projection on to a flat surface offers difficulty, and certainly gives rise to some error. As far as practicable, mechanical methods were employed, and errors in proportions are thereby greatly reduced. It is recognized that too much reliance cannot be placed on the details of the form of the suture-line for purposes of identification: ornamentation and proportions of the shell must have full consideration.

Suture-lines of the following species:—

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Fig. 1.—Baculites rectus n. sp. Bull's Point.
Fig. 2.—Ptychoceras zelandicum n. sp. Whangaroa.
Fig. 3.—Diplomoceras wakanene n. sp. Bull's Point.
Fig. 4.—Phylloceras nera Forbes. H. 19; W. 9. Batley.
Fig. 5.—Phylloceras bistriatum n. sp. H. 19; W. 19. Bull's Point.
Fig. 5a.—Internal suture-line.
Fig. 6.—Phylloceras forbesianum d'Orb. H. 17; W. 16.5. Batley.
Fig. 7.—Phylloceras radiatum n. sp. H. 22; W. 15. Bull's Point.
Fig. 7a.—Internal suture-line.
Fig. 8.—Phylloceras minimum n. sp. H. 10.5; W. 9.
Fig. 8a.—Internal suture-line.
Fig. 9.—Zelandites kaiparaensis n. sp. H. 7.6; W. 6. Bull's Point.
Fig. 9a.—Internal suture-line.
Fig. 10.—Schluteria rarawa n. sp. H. 4.75; W. 5.25. Batley.

Suture-lines of the following species:—

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Fig. 1.—Pseudophyllites indra Forbes. H. 22; W. 21. Bull's Point.
Fig. 2.—Pseudophyllites whangaroaensis n. sp. H. 16; W. 18. Whangaroa.
Fig. 3.—Gaudryceras politissimum Koss. H. 9; W. 7.5. Bull's Point.
Fig. 4.—Gaudryceras propemite n. sp. H. 7; W. 9.
Fig. 4a.—Internal portion of suture-line. Bull's Point.
Fig. 5.—Tetragonites margaritatus n. sp. H. 5.5; W. 6.25. Batley.
Fig. 6.—Tetragonites latus n. sp. H. 6.25; W. 10. Batley.
Fig. 6a.—Internal portion of suture-line. H. 4; W. 8.
Fig. 7.—Gaudryceras particostatum n. sp. H. 7; W. 6.5. Bull's Point.
Fig. 7a.—Internal portion of suture-line. H. 8; W. 8.
Fig. 8.—Gaudryceras subsacya n. sp. H. 5; W. 7.5.
Fig. 8a.—Internal portion of suture-line. H. 7; W. 9.
Fig. 9.—Vertebrites murdochi n. sp. H. 5; W. 10. Hokianga.
Fig. 9a.—Internal portion of suture-line.
Fig. 10.—Gaudryceras crenatum n. sp. H. 4.75; W. 6.5. Bull's Point.
Fig. 11.—Tetragonites simplex n. sp. H. 5.75; W. 5.5. Batley.
Fig. 11a.—Internal portion of suture-line. H. 3; W. 3.

Suture-lines of the following species:—

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Fig. 1.—Jacobites whangaroaensis n. sp. H. 44; W. 35. Whangaroa.
Fig. 2.—Jacobites angularis n. sp. H. 21; W. 22.5. Bull's Point.
Fig. 3.—Jacobites anderssoni K. & R. H. 12; W. 11.
Fig. 3a.—Internal portion of suture-line. H. 5; W. 5.
Fig. 4.—Neomadrasites nodulosus n. sp. H. 7.5; W. 9.25. Bull's Point.
Fig. 4a.—Internal portion of suture-line.
Fig. 5.—Jacobites minimum n. sp. H. 3; W. 2.2. Batley.
Fig. 6.—Madrasites multicostatus n. sp. H. 9.5; W. 10. Bull's Point.
Fig. 7.—Madrasites regularis n. sp. H. 10; W. 10. Bull's Point.
Fig. 8.—Gunnarites nordenskjoldi K. & R. H. 5; W. 5. Batley.
Fig. 9.—Brahmaites rotundus n. sp. H. 5; W. 8. Batley.
Fig. 10.—Tetragoniles tetragonus Koss. H. 16; W. 17. Bull's Point.
Fig. 11.—Pseudophyllites whangaroaensis n. sp. Internal portion of suture-line. H. 6.5; W. 7.5. Whangaroa.
Fig. 12.—Madrasites fortior n. sp. Whangaroa.

Suture-lines of the following species:—

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Fig. 1.—Gunnarites inflatus K. & R. H. 38; W. 32. Batley.
Fig. 1a.—Internal portion of suture-line H. 35; W. 31. Bull's Point.
Fig. 1b.—Suture-line of juvenile form. Bull's Point.
Fig. 2.—Gunnarites zelandicus Marshall. H. 24; W. 22. Specimen somewhat eroded.
Fig. 3.—Gunnarites antarcticus Stuart Weller. H. 35; W. 27. Batley.
Fig. 4.—Internal suture-line of Jacobites angulans n. sp. H. 21; W. 25.
Fig. 5.—Puzosia angusta n. sp. H. 25; W. 9.

Suture-lines of the following species:—

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Fig. 1.—Maorites tenuicostatus Marshall. H. 51; W. 35.5. Batley.
Fig. 1a.—Internal portion of suture-line. H. 39; W. 35.
Fig. 2.—Jacobites waitapuensis n. sp. H. 34; W. 30. Whangaroa.
Fig. 3.—Maorites suturalis n. sp. H. 26; W. 17. Bull's Point.

Suture-lines of the following species:—

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Fig. 1.—Maorites densicostatus K. & R. H. 21; W. 13. Bull's Point
Fig. 2.—Tainuia aucklandica n. sp. H. 43; W. 34. Whangaroa.
Fig. 3.—Parapuzosia brevicostata n. sp. Whangaroa.
Fig. 4.—Parapuzosia ordinaria n. sp. H. 8; W. 6. Batley.
Fig. 5.—Hauericeras ngapuhi n. sp. H. 9; W. 6. Bull's Point.
Fig 5a.—Internal portion of suture-line.

(Through an unfortunate error tubercles are indicated in fig. 3 in place of fig. 1.)

Suture-lines of the following species:—

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Fig. 1.—Acanthoceras ultimum n. sp. Bull's Point.
Fig. 1a.—Internal portion of suture-line. H. 9.
Fig. 2.—Parapachydiscus rogeri n. sp. H. 220; W. 270 (?). Bull's Point.
Fig. 3.—Nowakites denticulatus n. sp. H. 39; W. 38 (?). Bull's Point.

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Fig. 1.—Phylloceras nera Forbes. × 1 ½.
Fig. 2.—Phylloceras nera Forbes: section from periphery to umbilicus.
Fig. 3.—Phylloceras radiatum n. sp. × 1 ½.
Fig. 4.—Phylloceras radiatum n. sp.: section from periphery to umbilicus.
Fig. 5.—Phylloceras minimum n. sp. Bull's Point. × 2 ½.
Fig. 6.—Phylloceras minimum n. sp.: section.

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Fig. 1.—Phylloceras bistriatum n. sp. Bull's Point. × 2.
Fig. 2.—Phylloceras bistriatum n. sp.: section.
Fig. 3.—Phylloceras forbesianum d'Orb. × 2.
Fig. 4.—Phylloceras forbesianum d'Orb.: section.

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Fig. 1.—Gaudryceras politissimum Koss. Batley. × 1 ½.
Fig. 2.—Gaudryceras politissimum Koss.: section.
Fig. 3.—Gaudryceras propemite n. sp. Bull's Point. × 1 ½.
Fig. 4.—Gaudryceras propemite n. sp.: section.

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Fig. 1.—Gaudryceras subsacya n. sp. Bull's Point. × 1 ¼.
Fig. 2.—Gaudryceras subsacya n. sp.: section.
Fig. 3.—Pseudophyllites indra Forbes. × 1 ¼.
Fig. 4.—Pseudophyllites indra Forbes: section.
Fig. 5.—Pseudophyllites indra Forbes: flank, showing suture-line.
Fig. 6.—Tetragonites epigonus Koss. × 1 ½.
Fig. 7.—Tetragonites epigonus Koss.: section.

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Fig. 1.—Vertebrites murdochi n. sp. × 1 ½.
Fig. 2.—Vertebrites murdochi n. sp.: section.
Fig. 3.—Gaudryceras particoslatum n. sp. × 1 ½.
Fig. 4.—Gaudryceras particoslatum n. sp.: section.
Fig. 5.—Tetragonites margaritatus n. sp. × 1 ½.
Fig. 6.—Tetragonites margaritatus n. sp.: section

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Fig. 1.—Zelandites kaiparaensis n. sp. Bull's Point. × 1 ½.
Fig. 2.—Zelandites kaiparaensis n. sp.: section.
Fig. 3.—Gaudryceras crenatum n. sp. Bull's Point. × 1 ½.
Fig. 3a.—Gaudryceras crenatum n. sp.: section.
Fig. 4.—Brahmaites rotundus n. sp. Batley. × 1 ½.
Fig. 5.—Brahmaites rotundus n. sp.: section.
Fig. 6.—Parapuzosia ordinaria n. sp. Batley. × 1 ¼.
Fig. 7.—Parapuzosia ordinaria n. sp.: section.
Fig. 8.—Diplomoceras wakanene n. sp Bull's Point. × 1 ½.
Fig. 9.—Diplomoceras wakanene n. sp.: section.

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Fig. 1.—Tetragonites latus n. sp. Batley. × 1 ½.
Fig. 2.—Tetragonites latus n. sp.: section.
Fig. 3.—Tetragonites simplex n. sp. Bull's Point. × 1 ½.
Fig. 4.—Tetragonites simplex n. sp.: section.
Fig. 5.—Periphery of Pseudophyllites whangaroaensis n. sp., showing sculpture
Fig. 6.—Pseudophyllites whangaroaensis n. sp.: section.
Fig. 7.—Schluteria rarawa n. sp. Batley. × 1 ½.
Fig. 8.—Schluteria rarawa n. sp.: section.
Fig. 9.—Baculites rectus n. sp. Batley. × 1 ¼.
Fig. 10.—Baculites rectus n. sp.: section.
Fig. 11.—Ptychoceras zelandicum n. sp. Bull's Point. × 1 ½.
Fig. 12.—Ptychoceras zelandicum n. sp.: section.

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[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Oxybeloceras sp. Mangamuka River. Hokianga. × 3/2.

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Fig. 1.—Acanthoceras ultimum n. sp. Bull's Point. × 1 ¼.
Fig. 2.—Acanthoceras ultimum n. sp.: section.
Fig. 3.—Tainuia aucklandica n. sp.: showing development of tubercles. × 1 ¼.

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Fig. 1.—Madrasites multicostatus n. sp. Bull's Point. × 2.
Fig. 2.—Madrasites multicostatus n. sp.: section.
Fig. 3.—Madrasites regularis n. sp. Bull's Point. × 2.
Fig. 4.—Madrasites regularis n. sp.: section.

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Fig. 1.—Neomadrasites nodulosus n. sp. Bull's Point. × 1 ½.
Fig. 2.—Neomadrasites nodulosus n. sp.: section.
Fig. 3.—Neomadrasites nodulosus n. sp.
Fig. 4.—Jacobites angularis n. sp.: Bull's Point. × 1 ½.
Fig. 5.—Jacobites angularis n. sp.: section.
Fig. 6.—Gunnarites nordenskjoldi K. & R. Batley. × 1 ½.

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Fig. 1.—Jacobites whangaroaensis n. sp. Whangaroa. × ½.
Fig. 2.—Jacobites whangaroaensis n. sp.: section.
Fig. 3.—Jacobites anderssoni K. & R. Bull's Point. × 1 ½.
Fig. 4.—Jacobites anderssoni K. & R.: section.

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Fig. 1.—Madrasites sulcatus n. sp. Batley. × 2.
Fig. 2.—Madrasites sulcatus n. sp.: section.
Fig. 3.—Jacobites minimus n. sp. Batley. × 2.
Fig. 4.—Jacobites minimus n. sp.: section.
Fig. 5.—Nowakites denticulatus n. sp. Bull's Point. Nat. size.
Fig. 6.—Nowakites denticulatus n. sp.: showing costation. × 2.

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Fig. 1.—Gunnarites zelandicus Marshall. Batley. × 1 ½.
Fig. 2.—Gunnarites zelandicus Marshall: section.
Fig. 3.—Gunnarites antarcticus Stuart Weller. Bull's Point. × 1 ½.
Fig. 4.—Gunnarites antarcticus Stuart Weller: section.

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Fig. 1.—Gunnarites inflatus K. & R. Batley. Nat. size.
Fig. 2.—Gunnarites inflatus K. & R.: section.
Fig. 3.—Flank of Vertebrites murdochi n. sp., showing change in costation. × 5.

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Fig. 1.—Puzosia angusta n. sp.: showing costation. Bull's Point. × 2.
Fig. 2.—Puzosia angusta n. sp.: section.
Fig. 3.—Madrasites fortior n. sp. Whangaroa. × 2.
Fig. 4.—Madrasites cumshewaensis? Whiteaves. Whangaroa. × 2.

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Fig. 1.—Maorites tenuicostatus Marshall. Batley. Nat. size.
Fig. 2.—Maorites tenuicostatus Marshall (juv.). Bull's Point. × 2.
Fig. 3.—Maorites densicostatus K. & R. (juv.). Bull's Point.
Fig. 4.—Maorites suturalis n. sp. (juv.). Bull's Point. × 2.

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Fig. 1.—Maorites suturalis n. sp. Bull's Point. × 1 ¼.
Fig. 2.—Parapuzosia brevicostata n. sp. Whangaroa. × 2,
Fig. 3.—Hauericeras ngapuhi n. sp. Bull's Point. × 2.

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Fig. 1.—Jacobites waitapuensis n. sp. Whangaroa. × 1 ¼.
Fig. 2.—Maorites densicostatus K. & R. Bull's Point. Nat. size.

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Fig. 1.—Maorites tenuicostatus Marshall: section.
Fig. 2.—Jacobites waitapuensis n. sp.: section.
Fig. 3.—Hauericeras ngapuhi n. sp.: section.
Fig. 4.—Maorites densicostatus K. & R.: section.
Fig. 5.—Maorites suturalis n. sp.: section.
Fig. 6.—Parapuzosia brevicostata n. sp.: section.

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Fig. 1.—Tainuia aucklandica n. sp. Whangaroa. Nat. size.
Fig. 2.—Tainuia aucklandica n. sp.: fragment showing ornamentation. × 1 ½.
Fig. 3.—Taunuia aucklandica n. sp.: section.

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Fig. 1.—Parapachydiscus rogeri n. sp. Bull's Point. × ⅛. Fig. 2.—Parapachydiscus rogeri n. sp.: showing costation. × ⅓.

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So far as this collection is concerned, it has been found that the suture-line in nearly all cases has given clear indication of the generic position that a species should have, though it hardly enables one to distinguish between such genera as Madrasites, Jacobites, and Gunnarites. It is thought that the time that has been taken in drawing these lines in detail has not been wasted.

It seems that little attention has hitherto been given to the nature of the internal portion of the suture-line. In few researches on collections of ammonites have any drawings been made of them. So far as can be ascertained, Kossmat is the only author who has made any use of them for purposes of classification, and he appears to have done so in one instance only—in the distinction between Gaudryceras and Tetragonites.

In this paper drawings of the internal suture-line of several species will be found, and it is suggested that the form of it may be of great use in assigning species to their proper position in doubtful cases. Spath, however, attaches little or no importance to it: “The stretching-out of the auxiliary elements may only be the result of the adaptation of the suture-line to wider sides, and the raising of the umbilical portion is often found in younger developments” (53, p. 239). This, however, does not hold generally: compare, for example, Gaudryceras and Pseudophyllites.

The form of the internal suture-line is little varied in time and in the widely scattered species of a genus. The internal suture-line of a species of Phylloceras from the Dogger (Zittel, Handbuch, vol. 2, fig. 609) differs but little from those of New Zealand specimens from the Upper Cretaceous. The difference is almost restricted to a reduction in the number of saddles. It is certainly striking that the New Zealand species have the same number of saddles as in Sowerbyceras, and the suggestion thus offered that the New Zealand species should be placed in the latter genus is supported by some other details. Further material for study is, however, needed.

The genus Gaudryceras has the same unusual form of this suture-line in species from India, Japan, South Africa, and New Zealand. The importance of this line that is here suggested is supported by the great variety of form that it presents.

A summary of the variations that have been found in these New Zealand specimens is considered worthy of a special statement:—

Phylloceras: Internal saddle club-shaped. Two lateral saddles, the second with an almost spherical termination. No auxiliaries.

Gaudryceras: A single saddle of uniform width, which is typical in G. subsacya. Those species of Gaudryceras, such as G. semileve, which have a single saddle, increasing greatly in width at the base, should perhaps be placed in a separate genus.

Tetragonites: Two well-developed saddles, as in T. epigonus. Such a species as T. simplex has an additional saddle.

Pseudophyllites: Two saddles, the external one with much greater development than the first lateral.

Vertebrites: Five or six saddles, gradually decreasing in size towards the umbilicus.

Zelandites: A single saddle, wide at the base.

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Jacobites and Gunnarites both have two large saddles, which in the latter genus are much dissected; the antisiphonal lobe is very deep. This form appears to indicate a descent from Acanthoceras.

Madrasites, so far as the New Zealand specimens are concerned, has an internal suture-line but little different from Jacobites, and thus differs much from that figured by Kossmat.

The suture-line of Pachydiscus as drawn by Yabe is quite different from those of the genera mentioned, but it could not be seen in any of the New Zealand specimens.

Maorites, Puzosia, and Hauericeras have the same type of internal suture-line. The lateral saddles and the auxiliaries are situated on the outer slope of the internal saddle, and thus give the appearance of a single complex much-divided saddle. This type of internal suture-line appears as far back as Dalmasiceras, and is continued in Perisphinctes, and is supposed to indicate a relationship to the Hoplitid stock. It is much regretted that the material that was available did not allow of further study.