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Volume 56, 1926
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Madrasites Kilian and Reboul.

This was established by Kilian and Reboul in 1909 as a subgenus of Kossmaticeras, and was characterized by them in the following words (46, p. 25): “Un premier groupe comprend des formes, telles que K. karapadense Kossm. sp., K. bhavani Stol. K. theobaldianum Stol., qui conserve jusque dans l'adulte leur ornamentation caraéristique; nous designerons cette section sous le nom de Madrasites. Certaines formes, comme K. aemilianum Stol., prennent aussi, que l'a justment remarqué M. Kossmat, une ornamentation rappelant celle d'Astieria.”

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The New Zealand species that can be referred to Madrasites show no striking differences from these of South India which have been described and figured by Forbes, Stoliczka, and Kossmat. Several of them are clearly seen to be closely allied to Indian species, as will be stated in detail in the specific descriptions. It is interesting to find species that are considered to be closely allied to M. mooraviatoorensis Stol. and M. buddhaicum Kossmat in the same locality. These New Zealand species of Madrasites seem to be quite different from those described from Zululand and Pondoland by Spath (53, 54, 59), by van Hoepen from Pondoland (51, 52), from Japan by Yokoyama (17) and Jimbo (22), and, in my opinion, from those of Vancouver and of California. On the other hand, Madrasites tenuistriatus Paulcke from South Patagonia (36) is closely related to M. sulcatum n. sp., and at Seymour Island Kilian and Reboul recorded M. karapadense (46, p. 30).

Madrasites sulcatus n. sp. (Plate 38, figs. 1, 2.)

Dimensions :—

Diameter 33 100
Height of last whorl 13.5 43
Width of last whorl 12 36
Umbilicus 12 36

Shell discoidal and rather compressed. Whorls distinctly higher than wide. Involution about one-third. Umbilical slope very steep; the surface passes through 80° over a sharp curve. Lower half of flank slopes at first slightly outwards, then is almost flat, but soon slopes gently to periphery, over which it passes in a narrow curve.

There are three deep constrictions in a half-revolution, which always cut off three ribs. Each constriction has a prominent bolster on both sides. Ribs narrow and sharp, with wide interstices. They arise just above umbilical wall and hardly touch tubercles, which are numerous. There are forty-seven ribs in a half-revolution. Some of them begin quite close to an umbilical tubercle, but most of them originate rather higher on the flank and are almost straight. They do not fork, and are not tuberculate. Twelve umbilical tubercles in a half-revolution. Suture-line not sufficiently well shown to allow a satisfactory diagram to be drawn, but it can be seen that it does not differ very much from the other species of Madrasites

This species differs from all other known species of Madrasites. The relatively narrow aperture, close but straight ribs, and numerous tubercles are distinctive.

A single specimen has been found at Bull's Point. It was sent to Professor Kilian for examination, and he kindly sent the following note: “A new variety of Kossmaticeras nordenskjoldi K. & R.“

Madrasites multicostatus n. sp. (Plate 21, fig. 6; Plate 35, figs. 1, 2.)

Compare—

  • Holcodiscus buddhaicus Kossmat (28, p. 42, pl. 8, figs. 3 a, b, c).

  • Holcodiscus karapadensis Kossmat (28, p. 41, pl. 8, figs. 2, 4).

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.
Diameter 36 100 24.5 100 20 100 36 100 30 100
Height of last whorl 14.5 40 9.5 39 8 40 16 44 10.8 36
Width of last whorl 15.5 44 11 45 9 45 16.5 46 9.2 31
Umbilicus 13.5 37 9 37 8 35 11 31 11.5 38

A, B, C, Madrasites multicostatus from Bull's Point; D, Holcodisens buddhicus Koss; E, Holcodiscus kasapadensis Koss

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Shell moderate size with whorls that do not increase rapidly. Involution about one-third. Whorls rather wider than high, with a steep slope from umbilicus, then gradually curving to periphery, which is gently rounded.

Ornamentation: A row of nineteen or twenty tubercles, small and rounded, but varying considerably in size, situated at top of umbilical wall. From these arise a variable number of small rounded ribs, which follow a rather sinuous curve to periphery. At first they are directed slightly forwards, but after passing top of umbilical slope they bend backwards, and on edge of periphery they again bend forward and so continuing pass over periphery. Most of the ribs become quite indistinct in peripheral region. Interstitial ribs occasionally arise at various points. Here and there a number of fine striations can be seen parallel to the ribs. Sometimes striations occur on or between ribs, and sometimes they entirely displace them; in such cases they pass over periphery without interruption. Seven constrictions in last whorl. They arise from bottom of umbilicus and have a thick bolster on either side. They bend forward rather more than ribs, of which they intersect two or three. Constrictions form a conspicuous curve over siphuncle.

Suture-line quite typical of species of Madrasites so far as the main portion of it is concerned, but there is a sudden change of direction after second lateral saddle. The three auxiliary saddles are directed almost radially, and thus a most pronounced umbilical lobe is formed almost like that figured by Kossmat for H. bhavani (28, p. 38, pl. 8, fig. 5). In other respects, however, there is no resemblance between these two species.

Professor Kilian was good enough to examine the type of this species. In a note of a purely preliminary nature he classed it as Kossmaticeras buddhaicum n. var. multicostatum. I consider, however, that it is quite distinct from M. buddhaicum. The present species has a much higher whorl, and more distinct and fewer tubercles. Its ribs do not bifurcate nearly so frequently, and are more numerous—forty-two in place of thirty-one in a half-whorl. The ribs are more rounded and more often vanish on periphery. Suture-line is, of course, quite distinct from that of M. buddhaicum. Ribs in this species are not inclined forward as in M. karapadensis, and aperture is much wider. The constrictions are more numerous, being seven in number, compared with four in the Indian species. M. buddhaicum, which is probably the most closely allied species, is found in the middle horizon of the Trichinopoly group of the Indian occurrences.

Madrasites regularis n. sp. (Plate 21, fig. 7; Plate 35, figs. 3, 4.)

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 30 100 24 100
Height of last whorl 10.25 34 9 37
Width of last whorl 12 40 10.25 43
Umbilicus 12 40 10 42

A and B, Madrasites regularis, Bull's Point, Kaipara Harbour, N.Z.

These dimensions differ slightly from those of M. multicostatus, immediately preceding.

The most notable features are that the height is small and the umbilicus wide. Shell of moderate size, discoidal. Whorls wider than high. Umbilical wall steep but sloping. Flanks sloping gently to periphery, which is well rounded. Involution about one-half. Whorls not increasing rapidly in height or width.

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Ornamentation: Top of umbilical wall crowned with a row of fourteen to seventeen rounded tubercles. These are first noticed on second whorl at a diameter of 7 mm. From each of these tubercles rise two or three moderate rounded ribs, and usually two interstitial ribs begin at the same level in each interval. Ribs much narrower than intervening furrows, but height decreases slightly at periphery, which is crossed with a gentle forward curve. Four large and conspicuous constrictions in a revolution. They begin at bottom of umbilicus and are inclined forward more strongly than ribs, one or two of which they intercept. Constrictions bordered by a large bolster behind and a much smaller one before.

Suture-line in several features is not very different from that of M. multicostatus, but auxiliary saddles are less developed and umbilical lobe is not so conspicuous. Serrations of saddles more finely cut. External lobe wide and process at the bottom more developed. First lateral lobe extremely symmetrical.

This species is distinguished from M. multicostatus by the more regular umbilical tubercles, stronger and more continuous ribs, fewer constrictions, and much less pronounced forward curve of constrictions on periphery. When compared with the Indian species it is found that the shape of the whorl distinguishes it from M. karapadensis Kossm. (28, p. 41, pl. 8, fig. 4). Ribs more continuous, and have not the same strong forward bend at periphery as in the Indian species. Ribs not inclined forward so strongly as in M. bhavani (28, p. 41, pl. 8, fig. 4), which is probably different from Ammonites bhavani Stol. (11, p. 38, pl. 8, fig. 5). They are also less numerous, and the umbilical lobe is less pronounced. M. buddhaicus Koss. (28, p. 42, pl. 8, fig. 3) has less continuous ribs. Of the Indian forms this species resembles M. mooraviatoorensis Stol. most closely (11, p. 158, pl. 77, fig. 4), but the latter species has rather smaller tubercles, while its ribs are closer, the constrictions five to a whorl, and bent more strongly forward. Its suture-line is not dissimilar. This species is placed by Kossmat (28, p. 33) in his first division of Holcodiscus, which he says shows special relationship to the forms of this genus found in the chalk of Europe.

Three specimens have been found at Bull's Point and one at Whangaroa.

Madrasites fortior n. sp. (Plate 21, fig. 12; Plate 41, fig. 3.)

Dimensions:—

A
Diameter 13.5 100
Height of last whorl 5.5 41
Width of last whorl 6.4 47
Umbilicus 4 30

A, Madrasites fortior, Whangaroa Harbour, N.Z.

Shell of moderate size. Whorls nearly circular, increasing rapidly. Whorl rises rapidly from umbilicus and curves evenly into the rounded flank, which in its turn maintains the curve over periphery. Large and prominent smooth ribs, fifteen in a half-revolution, arise from tubercles at top of umbilical wall. Usually two arise from each tubercle, and there are rarely any interstitial ribs. They are inclined slightly forwards, and cross periphery with a slight curve and without any diminution in size. Seven constrictions in a revolution, and they have a stronger inclination than the ribs, but intersect only one of them. The bolster behind each rib is not larger than an ordinary rib. Constrictions cross ribs with a strong forward bow.

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Suture-line not well seen; it is apparently of the typical Madrasites form, but less dissected than in the other species.

Only three specimens of this species have been found, two of them very small and immature. There is only one (imperfect) specimen of a mature form. Two come from Whangaroa, the third from Bull's Point.

Madrasites sp. (Plate 41, fig. 4.)

A fragment from Whangaroa in some respects resembles M. cumshewensis. No suture-line could be developed.