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Volume 56, 1926
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– 141 –

Gaudryceras de Grossouvre (19, p. 225).

The following is the diagnosis of the genus given by de Grossouvre: “Ce genre est caracterisé par l'allure des striés de la coquille partant de l'ombili infléchies en avant, et par une ligne suturale formée de lobes et de selle assez nombreux, les lobes étant tous à terminaison paire.” He lays stress on the striae being directed back from the edge of the umbilicus. The sutural line is not so much reduced in auxiliaries as in Lytoceras. In the greater number of species the whorls increase slowly, and are but slightly involute in the young, but afterwards increase more rapidly, especially in height.

Kossmat later emended the description (28, p. 113). Slightly involute forms, with periodic constrictions forming bolsters on the shell or furrows on the cast. These, like the fine wire-like ribs, start at right angles to the umbilicus, and in the under half of the flank bend forward and in the upper half backward, forming a shallow forward bend on the periphery. The suture-line is of the greatest importance for the whole group. The median saddle is small, like a spear; the external lobe long and small, as deep as the first lateral lobe. The bifid external saddle is conspicuous. There are always several auxiliary lobes, which form a distinct umbilical lobe. In the internal portion there is a small and deep antisiphonal lobe, which goes as far back, or farther, than the umbilical lobe. A long tree-like saddle separates the two lobes, and on its side it is deeply dissected by sharp points. The bottom of the deep highly characteristic umbilical lobe is two-pointed, like the antisiphonal lobe. (Translation of extract.)

The nature of this internal suture-line separates Gaudryceras from Tetragonites. All species of Gaudryceras have at the base of the partition wall a single deep groove which corresponds in position to the antisiphonal lobe, while Tetragonites, with a greater number of internal lobes, has more than one on each side of the antisiphonal line.

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Gaudryceras propemite n. sp. (Plate 20, fig. 4; Plate 28, figs. 3, 4.)

Compare—

1865.

Ammonites sacya var. multiplexus Stol. (11, p. 155, pl. 76, fig. 1).

1866.

Lytoceras mite von Hauer, Neue Cephalopoden der Gosaugebilde, Sitz. Akad. der Wiss. Wien, Bd. 53, p. 7, Taf. 2, figs. 3, 4.

1873.

Ammonites sacya var. sachalinensis Schmidt (4, p. 15, Taf. 2, figs. 1, 2, 6.

1893.

Gaudryceras mite Hauer, in de Grossouvre (19, p. 227, pl. 26, fig. 4; pl. 39).

1895.

Gaudryceras jukesi Sharpe, in Whiteaves (27, p. 129, pl. 2, figs. 1, 2).

1895.

Lytoceras (Gaudryceras) multiplexum Koss. (28, p. 121, pl. 15, fig. 6).

1907.

Lytoceras varagurense var. patagonicum Paulcke (42a, p. 6, Taf. 17, figs. 1, 2).

1917.

Gaudryceras aff. jukesi (Whiteaves) Sharpe, in Woods (57, p. 35, pl. 20, fig. 2).

Dimensions:—

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

A. B. C. D.
Diameter 64 100 78 100 101 100 64 100
Height of last whorl 24 37 23 29 40 40 25 40
Width of last whorl 28 44 24 30 38 38 26 41
Umbilicus 19 30 38 49 35 35 24.5 39

A, Gaudryceras propemite, Bull's Point, Kaipara Harbour, N.Z.; B, Lytoceras (Gaudryceras) multiplexum Koss. (28, p. 121, Taf. 15, fig. 6); C, Lytoceras (Gaudryceras) varagurense (28, p. 122, Taf. 18, fig. 2, pl. 17, fig. 9): D, Lytoceras (Gaudryceras) vertebratum Koss. (28, p. 126, Taf. 15, figs. 4, 5).

The dimensions given above show that the breadth and height of the whorl are almost equal, and that they come nearest to G. vertebratum of the Indian species.

Form discoidal, with an involution of one-third. Seven whorls when diameter is 64 mm., with its greatest thickness just above slope to umbilicus; from this point there is a gradual slope to periphery, which is evenly rounded. Whorls slightly wider than high; whorls do not increase rapidly in height.

Ornamentation: A large number of rounded ribs of moderate size, which on body-chamber begin rather indistinctly near base of umbilical wall. They rapidly increase in distinctness, and at top of umbilical slope many divide into two, and other interstitial ribs arise, their number being increased about twofold. Ribs at first almost radial, but soon bend strongly forward, then distinctly backward, and at periphery again slightly forward so that they cross it with a slight forward curve. Ornamentation of inner whorls the same up to the point where they are covered by the next succeeding whorl; here they break up into striations, and similar additional striations arise interstitially and cross periphery with a slight forward bend. There are periodic furrows, sometimes very distinct, about four in a whorl.

Suture-line does not differ to any important extent from that of the different coarse-ribbed forms of Gaudryceras from South India which have been mentioned above. On the whole, it is rather more like that of G. vertebratum than the others. The most distinctive character is in the development of the median secondary saddle in the first lateral lobe.

The species is evidently very close to the G. vertebratum-varagurense group in all respects, but in none of them is there any mention of the curious change in the nature of the sculpture in all of the inner whorls. Gaudryceras cinctum Spath, from Pondoland, is also close, as is G. mite Hauer, from the Santonian of Europe. Again, G. varagurense var. patagonica Paulcke, from Patagonia, is closely related, but the details of the ornamentation seem to be distinct. G. varagurense and G. mite have been recorded by Kilian and Reboul from Seymour Island, but in both cases

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it appears that the state of preservation does not allow any details of the ornamentation to be seen.

A single complete specimen has been found at Bull's Point, as well as several fragments.

G. multiplexum and G. vertebratum come from the Utatur formation, and G. varagurense from the Upper Trichinopoly (= Lower Senonian) of Europe.

Gaudryceras particostatum n. sp. (Plate 20, fig. 7; Plate 30, figs. 3, 4.)

Compare—

1906.

Gaudryceras kayei Forbes, in Woods (40, p. 335, pl. 41, fig. 8).

1921.

Gaudryceras varicostatum van Hoepen (52, p. 7, pl. 2, figs. 10–12, text-figs. 3, 4).

1922.

Gaudryceras varicostatum van Hoepen, in Spath (54, p. 117).

Dimensions:—

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

A. B. C. D.
Diameter 27 100 24 100 33 100 39.6 100
Height of last whorl 10 37 9 38 13 39 13.7 35
Width of last whorl 10 37 9 38 11 34 14.7 37
Umbilicus 10 37 11 45 13 39 17.2 43

A, B, C, Gaudryceras particostatum, Bull's Point, Kaipara Harbour, N.Z.: D, Gaudryceras varicostatum van Hoepen (52, p. 7).

The dimensions show at once that height and width of whorl are almost equal, and umbilicus extremely wide. Shell small, with whorls that show little involution and do not increase rapidly in size. Umbilicus wide, with a nearly uniform slope. When the radius is 14 mm. six whorls are developed. The umbilical slope is steep, but passes by a rapid curve into the flank, which slopes steeply to the well-rounded periphery.

Ornamentation: Flanks of inner whorls covered with thin wire-like ribs, which begin at umbilicus and at once bend sharply forward. At edge of periphery, where whorl is covered by the succeeding one, the wires change into a number of minute striations, which require a high-powered lens to show them up. These have a slight bend forward where they cross periphery. On body-chamber the wire-like ornamentation cannot be seen, and its place is taken by fine striations; these are not easily seen, and without a careful inspection the surface appears to be smooth. Four conspicuous constrictions in a revolution.

Suture-line in both external and internal portions very similar to that of Gaudryceras varicostatum. Antisiphonal lobe differs from typical form in its greater breadth. External portion of suture-line is quite typical of the genus, though, on the whole, it is perhaps rather less deeply dissected. Umbilical lobe unusually deep and extremely steep. The width of the single saddle in the internal portion of the suture-line is noticeable, and in this respect this species resembles G. propemite, G. varicostatum, and G. varagurense, though it is less marked in the last species.

This species certainly comes nearer to Gaudryceras varicostatum than to any other that could be found in the available literature. It is, however, distinguished by the finer ribbing and the somewhat higher whorl. There seems to be no Indian species to which it shows a close resemblance, for it has a higher whorl and smaller umbilicus than G. multiplexum; finer ribbing and a wider umbilicus than G. varagurense; a narrower and lower whorl than G. vertebratum, and finer ribbing as well; and in none of these species has it been recorded that the ribbing changes in its character on the upper part of the flank.

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Several good specimens have been obtained at Bull's Point, and one in poor condition from Whangaroa. In the Auckland Museum there is a specimen in good condition labelled as coming from Morant's Island, in the Kawhia Harbour. This, however, I regard as a mistake, as the rocks on that minute island are entirely Tertiary in their age. It is possible that this and Baculites rectus n. sp., which have the same matrix, come from Hokianga or from Kaipara.

Gaudryceras subsacya n. sp., (Plate 20, figs. 8, 8a; Plate 29, figs. 1, 2.)

Compare—

  • Ammonites sacya Forbes (1, p. 113, pl. 14, fig. 10).

  • Ammonites buddha Forbes (1, p. 112, pl. 14, fig. 9).

  • Ammonites sacya Forbes, in Stol. (11, p. 154, pl. 75, figs. 5–7; pl. 76, figs. 1, 2, 3).

  • Ammonites sacya var. sachalinensis Schmidt (4, p. 15, pl. 2, figs. 3, 4).

  • Ammonites filicinctus Whiteaves (7, p. 43, pl. 2, figs. 2, 3).

  • Lytoceras sacya Forbes, in Whiteaves (7, p. 203, pl. 25).

  • Lytoceras sacya Forbes, in Yokoyama (17, p. 178, pl. 18, fig. 12).

  • Lytoceras sacya Forbes, in Jimbo (22, p. 34, pl. 6, fig. 1).

  • Lytoceras sacya Forbes, in Stanton (20, p. 445).

  • Lytoceras (Gaudryceras) sacya Forbes, in Koss. (28, p. 119).

  • Lytoceras (Gaudryceras) sacya Forbes, in Anderson (33, p. 82).

  • Gaudryceras tenuihratum Yabe (48, p. 19, pl. 3, figs. 3, 4; also var. ornata, pl. 3, fig. 2).

  • Gaudryceras striatum var. pictum Yabe (48, p. 33, pl. 4, fig. 3).

  • Gaudryceras sacya Forbes, in Woods (57, p. 11, pl. 5, figs. 4 a, b).

  • Lytoceras sp. Marshall (49, p. 445, pl. 33, fig. 3, text-fig. 4).

  • Gaudryceras sacya Forbes, in Spath (59, p. 54).

Dimensions:—

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

A. B. C. D. E. F. G.
Diameter 28 100 22.75 100 36 100 29 100 24 100 16 100 45 100
Height of last whorl 10.5 37 9 39 12.5 35 11 38 9 37 6.2 39 33
Width of last whorl 10.75 42 10.25 45 14 39 12 41 10.25 42 8 50 34
Umbilicus 11.5 41 10 44 13.5 38 11.25 39 9 37 7 44 44
H. J. K. L. M. N. P.
Diameter 95 100 40 100 50 100 120 100 113 100 300 100 35 100
Height of last whorl 43 30 34 40 50 44 160 53 12 34
Width of last whorl 36 35 30 38 45 40 165 53 13 38
Umbilicus 32 50 46 36 36 32 55 18 15 42

A, B, C, D, E, F, Gaudryceras subsacya, Bull's Point and Batley, Kaipara Harbour, N.Z.; G, H, J, K, L, Gaudryceras sacya Forbes, in Stolicka (11, p. 154, pl. 75, figs. 5–7; pl. 76, fig. 23); M, Gaudryceras sacya Forbes, in Kossmat (28, p. 119); N, P, Gaudryceras tenuiliratum Yabe (37, p. 19).

The six specimens of G. subsacya that were measured show at once that the species always has a whorl that is wider than high, and that the larger specimens are both lower and narrower than smaller ones. The Indian specimens that were measured by Stoliczka are in most cases higher than wide, and this is also the case in the Indian specimen quoted by Kossmat. Yabe's measurements of Gaudryceras tenuiliratum are much higher and wider in the large specimens than in the smaller. The measurements show that species is characterized by its uniformly wide whorl.

Shell discoidal with wide umbilicus, downward slope of which is modified by rounded contour of inner whorls. Involution about one-third. Slope from umbilicus steep, and gradually rounds off into flank; periphery flattened. Well-preserved specimens show five distinct constrictions marked

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on shell by prominent rounded ribs, which have a large furrow behind and a smaller one in front. Regular sculpture consists of extremely numerous ribs, so fine that when radius is 7 mm. there are 45 on an arc of periphery 5 mm. in length. Large ribs that mark constrictions are covered with these fine ribs, which arise at bottom of umbilical slope and at first have a slight forward inclination. This soon becomes pronounced, but decreases again at about two-thirds of distance from umbilicus. Ribs cross periphery with the very slightest forward bend. Near top of umbilical slope an interstitial rib arises between each pair, and all continue without interruption across periphery. Ribs and sculpture on body-chamber differ in no respect from those on younger whorls, except in size, which increases proportionately to diameter.

Suture-line is typical of the smaller species of Gaudryceras, and by itself can hardly be distinguished except by the slightly displaced position of the small secondary saddle in the first lateral lobe. Internal portion of suture-line also is quite typical of these smaller species, and shows the long and narrow single saddle which Kossmat considers an essential feature of the genus.

The position of this species is very close to G. tenuiliratum var. ornatum of Yabe; but comparison of the measurements shows that the whorl is both higher and wider than in the Japanese species, and at the same time the umbilicus is narrower. The resemblance to G. striatum var. pictum of Yabe is also close, but the ribs appear to be much more flexuous in that species. The specimens considered to be G. sacya by Yokoyama and Jimbo are differently classed by Yabe. Crick's specimen of G. pulchrum in the South Kensington Museum was also compared with those from New Zealand, and it was found that its ribs were distinctly sharper and farther apart than in the present species. Forbes's type of G. sacya is also in the Museum, and though it is in poor condition it is clear that the ribs are a little larger and farther apart than in the New Zealand examples. The species appears to be very similar to G. filicinctus of Whiteaves from the Queen Charlotte Islands. The examples here described from the north of New Zealand are quite close to the specimen from the Clarence Valley of the South Island of New Zealand, which was classified by Woods as G. sacya, for the only observable difference in that the ribs in the South Island specimen are rather coarser than those of all but one of the specimens from the North Island.

This species is common at Batley and at Bull's Point in the Kaipara Harbour, but no specimens were found at Whangaroa.

Gaudryceras sacya comes from the Lower Utatur group. No specimen yet found in New Zealand shows the corrugations which characterize the mature forms of G. sacya as figured by Whiteaves and of G. limatum figured by Yabe.

Gaudryceras politissimum Kossmat. (Plate 20, fig. 3; Plate 28, figs. 1, 2.)

Compare—

1895.

Gaudryceras politissimum Koss. (28, p. 128, Taf. 15, figs. 7 a-c).

1907.

Lytoceras (Gaudryceras) politissimum Koss., in Kilian and Reboul (46, p. 14, pl. 1, figs. 7, 8).

Dimensions:—

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

A. B.
Diameter 48 100 89 100
Height of last whorl 20 49 33 37
Width of last whorl 14 29 28 31
Umbilicus 16 33 34 38

A, Gaudryceras politissimum Koss., Bull's Point, Kaipara Harbour, N.Z.; B, Gaudryceras politissimum Koss. (28, p. 128).

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These dimensions show that the only specimen that is in good enough condition to be measured has a whorl a little higher than that of Kossmat's type, while the umbilicus is distinctly narrower. Comparisons with the dimensions of G. subsacya show that the whorl in that species is not so high as, but is much wider than, that of G. politissimum. In the specimen that has been measured the greater part of outer whorl is somewhat compressed. The inner whorls increase a good deal in their relative width, the penultimate whorl measuring—height, 4.5 mm.; width, 5.5 mm.; and the whorl next to that—height, 2.5 mm.; width, 3.5 mm. The broadest part of outer whorl is at top of umbilical wall, where there is a sharp curve to the gently sloping flank; but at periphery the curve is much sharper.

Ornamentation: Five constrictions can be distinguished in the last whorl, which appear as rounded ribs on the shell. They are low where they leave umbilicus. They at once bend forward and increase in size, but the forward curve is soon reduced, and they cross periphery with a slight forward bend. At first sight the surface of the shell appears to be polished, but when examined with a lens a number of regular but extremely fine hair-like ribs can be distinguished. About every tenth or fifteenth of these is larger. They start almost straight from the umbilicus, or with a slight backward trend. They soon bend forward on the edge of umbilicus; then they straighten up, but pass over periphery with a broad forward curve.

Suture-line agrees fairly well with that of G. politissimum figured by Kossmat. The saddles, however, are less divided, the slope to umbilicus begins sooner, and there are fewer auxiliary saddles; umbilical lobe is also deeper.

The specimen agrees quite well with description that has been given by Kossmat, though the relative height and width of inner whorls are not referred to by him. The ornamentation and also the form of G. politissimum, G. subtilineatum Koss. (28, p. 123), and G. valudayurense Koss. (28, p. 127) are very similar, but it appears that the ornamentation of the surface of G. valudayurense is rather stronger and the suture-line is rather more divided. It would be extremely difficult to distinguish the inner whorls of the New Zealand specimen of G. politissimum from those of G. subtilineatum described by Kossmat.

One specimen, in moderately good condition, from Bull's Point, and a second, of the inner whorls only, from Batley.

Gaudryceras crenatum n. sp. (Plate 20, fig. 10; Plate 31, figs. 3, 3a.)

Dimensions:—

A.
Diameter 27 100
Height of last whorl 9 33
Width of last whorl 10 37
Umbilicus 12 44

A, Gaudryceras c [ unclear: ] enatum, Bull's Point, Kaipara Harbour, N.Z.

Shell discoidal, with wide umbilicus which has very even slope. Involution about one-third. A steep even slope of umbilical wall, which curves rather quickly into flank, and therafter a uniform curve which passes without interruption over rounded periphery.

Ornamentation: Four shallow periodic furrows in last whorl, with occasionally a low rounded rib behind. The surface appears bright and shining, but examination shows that it is closely covered with fine thread-like ribs. These arise at umbilicus and are at first straight, but soon bend

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forward and maintain this direction until they reach beyond umbilical edge; they then bend slightly backwards, but soon again bend forward and pass with a broad curve across periphery. Ribs become less distinct at periphery, but there are no interstitial ribs. Ribs have a sharp crest, but are distinctly crenate on backward side. A good specimen and a high-power lens are necessary to reveal this structure.

Suture-line not well seen. Saddles not so highly divided as in the other species of Gaudryceras. External lobe is perhaps a little deeper than usual, and three auxiliary lobes are present.

Three specimens only, two of which come from Bull's Point and one from Batley.

The crenation of the small ribs is the most distinct characteristic of this species. So far as Cretaceous species of this family are concerned, it has been recorded only in Lytoceras mahadeva Stol., from the Lower Utatur of India; L. batesi, from the lower beds of Queen Charlotte Island of British Columbia; and L. ezoense, from the Lower Ammonite beds of Japan. These are included in the Lytoceras fimbriatum group of Kossmat, which is mainly distinguished by the absence of auxiliary lobes and saddles in suture-line (28, p. 112). The present species has three auxiliary lobes and saddles and at the same time its small size and fine ribbing ally it rather to the Gaudryceras group. It is perhaps permissible to regard the crenation as a vestigial remnant that shows clearly the lytoceratid ancestry.