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| A. Adult under 75 mm. long, posterior margin closed. | |
| (I) Medial ribs equal to or narrower than interstices. | |
| (a) Adult under 40 mm. long | brunneri |
| (b) Adult over 50 mm. long | |
| (1) Main ribs numbering 40–47 | waitakiense |
| (2) Main ribs numbering 37 | olssoni |
| (II) Medial ribs much broader than interstices | subcordatum |
| B. Adult over 75 mm. long, posterior margin gaping. | |
| (1) Medial ribs about equal to interstices | greyi |
| (2) Medial ribs much broader than interstices | cantuariense |
Hedecardium brunneri (Hector). (Plate 36, Figs. 9, 11.)
1886. Cardium brunneri Hector, Outline N.Z. Geol. p. 58. f. 20, no. 5.
1915. Suter, Alph. Handlist: 6.
1917. Cardium (Fragum) priscum Suter. N.Z.G.S. Pal. Bull. 5, p. 77, pl. 10, fig. 6.
Shell somewhat small, subcircular, beaks fairly prominent, moderately inflated. Sculpture of about 40 strong, rounded, main radial ribs with deep interstices of about the same width; posterior area probably with about 12 flat ribs with linear interstices.
Height, 30 mm.; length, 34 mm.; inflation (1 valve) 11 mm.
The shell is somewhat distorted. originally it was more nearly circular.
Localities: G.S. 29, Island Sandstone, Brunnerton (type). G.S. 45, Sandstone below limestone, St. Kilda, Brighton, West Coast. G.S. 1593, Millerton Colliery, West Coast, 150 feet above coal, Kaiata Mudstone. G.S. 27, Ten Mile, Greymouth, Island Sandstone. Near Kiwi Compressor. Denniston Colliery, West Coast, Kaiata Mudstone. G.S. 578, Greensand below limestone, Kakahu River. G.S. 480, Concretionary sandstone below greensand Waihao River. G.S. 176, Sandstone above coal beds, Black Point, North Otago. G.S. 2119, Concretions in silts, Green Valley, Waihemo S.D. G.S. 41, “Black Limestone, Tokomairiro,” Otago.
This species, frequently mentioned in the early discussions of West Coast stratigraphy, has not previously been described, its only claim to legality being a crude figure and a good locality. These are quite sufficient for recognition, within somewhat wide limits, but better specimens from the type locality may, some day, be found. A specimen from G.S. 29, Brunner Mine, from beds overlying the coal has been chosen as lectotype (Pl. 36, Fig. 9). It is accompanied by an old Colonial Museum label and presumably was identified as C. brunneri by Hector; it probably represents original syntype material.
Hedecardium waitakiense (Suter). (Pl. 35, Figs. 1, 2, 5.)
1907. Cardium (Trachycardium) waitakiense Suter, Proc. Mal. Soc., vol. vii, p. 209, pl. 18, fig. 6.
1915. Suter. N.Z.G.S. Pal. Bull. 3, p. 59, pl. 8, fig. 20.
Suter described this species from the fragment of a right hinge. A complete specimen of each valve as well as a number of hinge fragments were collected by the writer from the type locality, so that Suter's description can now be amplified. The ribs number about 40; they are flattened on top and separated by regularly rounded interspaces. On about juvenile half of shell medial ribs are wider
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than interspaces, but on adult, interspaces are wider than ribs; flattened tops of main ribs are smooth and glossy, but interspaces bear close, fairly regular but somewhat undulating concentric growth-ridges. Posterior, which is glossy throughout, bears about 14 of the peculiarly differentiated, flattish ribs. In juvenile these ribs are not raised and several of the anterior ones bear a shallow longitudinal furrow; they are separated by linear grooves set with small tubercles which are really developed on anterior side of each rib. In adult, ribs become raised, at first strongly bevelled, steep face anterior, but finally more rounded, and there are no tubercles.
Localities: “Greensand, Wharekuri” (type); G.S. 476, Kekenodon Beds, Wharekuri; G.S. 1821, north bank, Waitaki River, opposite Wharekuri; G.S. 1913, Shell Gully, Kelly's farm, Chatton; G.S. 2108, Greensand, Te Raumaku School, 2 ½ miles west of Otorohanga; G.S. 526, 1027, Okoke, Pirongia S.D. (Duntroonian).
Hedecardium olssoni, n.sp. (Pl. 35, Fig. 6; Pl. 37, Fig. 25)
Shell of moderate size, like waitakiense but differing in having only 37 instead of from 40–47 ribs. Main ribs noticeably higher and broader than those of waitakiense, but relationship of rib to interstice on different parts of disc about the same Shell shape also differs, posterior end being more truncate and whole shell more stoutly built.
Height, 61.5 mm.; length, 62 mm.; inflation, 23 mm.
Locality: G.S. 1913, Shell Gully, Kelly's Farm, Chatton (Duntroonian)
Although this shell is of the same age as waitakiense, the fewer triangular ribs and wide interstices justify separation. The number of ribs is much the same as that of subcordatum, but the wide interspaces between the sharply ridged ribs characterise olssoni. The species is named in honour of Mr Axel A. Olsson, of Gloversville, New York, with whom the writer spent a most pleasant collecting trip.
Hedecardium subcordatum (Suter).
1917. Cardium subcordatum Suter, N.Z.G.S. Pal. Bull. 5, p. 77, pl. 10, fig. 7.
Only the holotype of this species is known. It has about 37 main ribs and 12 posterior ones. The main ribs have flattened tops and are about twice as wide as the interstices.
Locality: Suter gave in his original description “Shell-bed at base of ‘Pareora’ beds, junction of Porter and Thomas Rivers, Trelissick Basin” and the accompanying label says “Trelissick Basin B.” (See Pal. Bull. 8, p. 50.) A good deal of matrix adheres to the specimen and since it is tuffaceous, the locality is wrong. The tuff consists of greenish grey much weathered volcanic fragments set in a good deal of secondary calcite, and is the same in appearance as the tuffs between limestones at the junction of the Porter and Thomas Rivers. Also adhering to the holotype, and shown in the original photo, is a specimen of Modiolaria elongata (Hutton), a species occurring commonly at this locality and not in the shell bed overlying the upper limestone. It is quite clear then that the true locality is “Tuffs between limestones, junction of Porter and Thomas Rivers.” The faunules of this bed, both Foraminiferal
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(H. J. F.) and Molluscan are of unusual facies, so correlation is not obvious, but probabilities indicate Duntroonian.
Hedecardium greyi (Hutton). (Pl. 35, Fig. 4.)
1873. Cardium greyi Hutt. Cat. Tert. Moll., p. 23.
1915. Suter, N.Z.G.S. Pal. Bull. 3, p. 59, pl. l, fig. 3.
1929. C. (Trachycardium) greyi Pow. & Bart., Trans. N.Z. Inst., vol. lx, p. 408, figs, 35, 36, 39, 40.
It is doubtful whether cantuariense can be maintained as a distinct species from greyi. Probably the question can be definitely settled only by statistical methods which must wait on the accumulation of numbers of specimens. Members of the group occur at a number of localities from the Waitakian to somewhat above the Awamoan. They are very large shells, some exceptionally large, differing from the earlier species of Hedecardium not only in greater size and shell-thickness, but also in having a pronounced posterior gape. As shown by the growth lines, this gape develops at an early stage, well before half the adult diameter is reached.
Kyeburn shells have fairly well-rounded ribs throughout, as also do the fragments from Otiake. Law's figures of cantuariense on the other hand, show considerable flattening of the adult medial ribs, accompanied by a relative narrowing of the interstices. A fine left valve from Ardgowan has flattened ribs like cantuariense, but it is smaller (79 × 80 × 35 mm.) yet is more inflated and regularly globose than usual for members of the group which generally become oblique with maturity. Oneroa shells seem to be somewhat variable in medial rib-width as also are the Mangapakeha ones which, incidentally, measure up to 145 × 150 × 60 mm. The Mokau and Clifden shells seen are poorly preserved, but in general their medial ribs tend to be flattened. From this it appears that flattening of the medial ribs and relative narrowing of the interstices may perhaps be used to separate stratigraphic species.
Hedecardium cantuariense (Laws). (Pl. 35, Fig. 3.)
For remarks see previous species.
Locality: Sutherlands, South Canterbury (type); G.S. 1985, shell bed, Ardgowan, North Otago.