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Volume 58, 1928
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– 157 –

Graptolites from Cape Providence, Chalky Inlet, Southland.

By Robert E. Keble.
(Communicated by Professor James Park.)

[Read before Otago, 9th November, 1926; received by Editor, 27th November, 1926; issued separately, 13th August, 1927.]

In 1922 graptolites were found by Professor James Park at Cape Providence, Chalky Inlet, Southland. * The graptolites are preserved as a film on dark blue pyritic nodular slate, highly cleaved, and suggesting the close proximity of an anticline. Some specimens show detail, but the majority are indistinct and were cleared with difficulty when the occasion arose. In the collection is one new species and probably another. Owing to the fact that there was only one form of the second species in the collection it has been flgured as Didymo-graptus sp.; the figure will be useful for comparison while searching for other specimens of the species.

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Fig. 1. —Didymograptus bidens n. sp. Polypary X 4. Spec. 27.
Fig. 2. —D. bidens n. sp. Sicula and Theca 12 X 6. Spec. 4 (reverse of Type Spec. 27)
Fig. 3. —D. sp. Polypary X 4. Spec. 88.

Didymograptus bidens n. sp.

Description: Branches arising suborally, gracefully curved for the first two thecae (Th 11, 12, 21 and 22), then divergent and lying within an angel of 25° Minimum width near the sicula, under 0.2 mm.; maximum width 0.8 mm.; maximum length observed 5 mm.

Sicula about 1.7 mm. long.

Thecae 8 or 9 in 10 mm., about twice as long as broad and free for four-fifths of their length. Apertural margins straight or slightly convex, submucronate, inclined at an angle of approximately 100° to the axis of the branch. Ventral margin concave.

[Footnote] * J. Park, “Discovery of Graptolites at Cape Providence, Southland.” N. Z. Journ. Sc. & Tech., vol. 5, p. 264, 1922.

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Remarks: The polypary is slender in appearance. There is little doubt that the branches arise suborally slightly below the sicula aper-ture. In both D. bidens and its undescribed Australian equivalent, specimens frequently show the branches from different angles, sug-gesting that they may not have been in the same plane.

Affinities: D. bidens appears to be the first of a characteristic series of dependent Didymograpti to be described. I know of no other dependent form like it figured elsewhere. In Victoria there is, however, an underscribed closely allied form, with a similar insignifi-cant thecal overlap and relatively wide submuceronate thecae. It is found with the same associates as D. bidens.

Didymograptus sp.

Spec. 88 shows a form of Didymograptus which I cannot compare with any known form. The origin of the branches is apical; they are very slightly curved in the first thecae, then become straight and highly divergent, the normally compressed branch indicating an angle of 110° Their maximum width is 0.8 mm.; minimum width under 0.2 mm.; maximum length observed about 8 mm.

The sicula is 1.5 mm. long and tapering.

Thecae 9 to 10 in 10 mm. less than twice as long as wide, free for three-quarters of their length. Apertural margin straight or slightly concave at an angle of 105°, to the axis of the branch. Ventral margin slightly concave, inclined at an angle of 45°.

As there is only one example in the collection, I have refrained from elevating it to specific rank, preferring to await the discovery of others. The thecae are of the D. bidens type, but the origin of the branches is distinctly apical and the divergent angel considerable.

The New Zealand faunal province lying between that of Australia on the east, and America on the west, an interesting comparison is forthcoming by tabulating the species on a common basis.

Species common
to N. Zealand.
Australia, and
America.		 Species
common to
N. Zealand
and Australia.		 Species
restricted
to
N. Zealand.		 Genera
common to
N. Zealand
and Australia.
D. bifidus +
D. extensus +
D. caducens +
T. pendens +
T. serra +
T. similis +
T. amii +
T. quadribrachiatus +
D. octobrachiatus +
D. procumbens +
D. adamantinus +
T. whitelawi +
D. bidens +
Clonograptus sp. +
Goniograptus sp. +
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Considering that D. bidens has its equivalent in Australia and that D. procumbens, D. adamantinus and T. whitelawi were hitherto regarded as restricted Australian forms, the similarity between the New Zealand and Australian fauna must be close. The Cape Providence beds could be accurately placed in the Australian Lower Ordovician, Castlemaine Zone, Subzone C4. Its Australian position is given to afford a means of checking the points of agreement and inevitable discrepancies between the two faunas. I have little doubt, however, that the points of agreement will be numerous.

List of Species.

  • Didymograptus bifidus J. Hall. 7, 17, 21, 23, 25, 26, 30, 34, 36, 41, 46, 53, 60, 61, 62, 63, 64.

  • D. cf. bifidus. 48, 61.

  • D. extensus J. Hall. 1, 27, 72, 74, 79, 86.

  • D. cf. extensus. 4, 11.

  • D. procumbens T. S. Hall. 23, 26, 59, 60, 74.

  • D. cf. procumbens. 28, 41, 65.

  • D. adamantinus T. S. Hall. 26, 45, 54, 80.

  • D. cf. gracilis Torn. 35.

  • D. caduceus Salter. 3, 10, 12, 13, 14, 18, 19, 23, 25, 29, 32, 35, 38, 44, 60, 72, 74, 78, 79, 80, 81, 83, 85, 86.

  • D. cf. caduceus. 16.

  • D. sp. 11, 15, 16, 18, 20, 23, 34, 37, 46, 52, 58, 78, 84, 85.

  • D. sp. nov. 4, 27, 88.

  • Tetragraptus pendens Elles. 16 (?), 37 (?), 67 (?).

  • T. serra Brong. 13, 15, 16, 33, 35, 46, 49, 54, 64, 69, 70, 77, 79.

  • T. cf. serra. 10, 82, 85.

  • T. similis, J. Hall. 37, 38, 57, 60, 70, 78, 79, 86.

  • T. amii Elles & W. 19, 25, 55.

  • T. cf. amii. 11.

  • T. whitelawi T. S. Hall. 30, 57, 67.

  • T. cf. whitelawi. 50.

  • T. quadribrachiatus J. Hall. 30, 36.

  • T. cf. quadribachiatus, 36.

    • T. sp. 61.

    • Dichograptus octobrachiatus J. Hall. 11.

    • Clonograptus sp. 33, 87.

    • Diplograptus sp. 71 (?).

    • Phyllograptus cf. angustifolius J. Hall. 31, 62, 73.

    • P. sp. 8, 12, 38, 71, 73, 78, 86.

    • Goniograptus sp. 54 (fragment).

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