. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. /N. Figure 28. Diagrammatic representation of the sutures of several species of Svalbardiceras. A, topotype of Sva/bard/'ceros schmtdti (Mojsisovics), from Olenekites Zone, Olenek region, Siberia, at c whorl height of 13 mm (Popov, 1961: 39, fig. 6b); B, Svo/bord/ceros sp. indet., from Upper Thoynes Formation, Hammond Creek, southeastern Idaho, at a whorl height of 15 mm (MCZ 9488); C, holotype of Svalbardiceras s/ieldon/ n. sp., from Co/umbifes fauna, Thaynes Formation, Draney Creek, southeastern Idaho, at a diameter
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. /N. Figure 28. Diagrammatic representation of the sutures of several species of Svalbardiceras. A, topotype of Sva/bard/'ceros schmtdti (Mojsisovics), from Olenekites Zone, Olenek region, Siberia, at c whorl height of 13 mm (Popov, 1961: 39, fig. 6b); B, Svo/bord/ceros sp. indet., from Upper Thoynes Formation, Hammond Creek, southeastern Idaho, at a whorl height of 15 mm (MCZ 9488); C, holotype of Svalbardiceras s/ieldon/ n. sp., from Co/umbifes fauna, Thaynes Formation, Draney Creek, southeastern Idaho, at a diameter of 38 mm (MCZ 9493); D, Svalbardiceras spitzbergemis (Frebold, 1929a: pi. 1, fig. 13; PI. 26, figs. 3, 4 of this report), from upper Scythian beds. Cape Thordsen, Spitsbergen, at a diameter of 37 mm. sp. indet., which I believe to be conspecific with the holotype, came from Cape Thord- sen. The specimens described in 1930 by Frebold came from Afj^ardh Bav, Milne Edwardsberg, and Botneheia (Corrie Down). All these specimens came from what is interpreted as a late Scythian horizon. The specimens from Cape Thord- sen were associated with a KcyscrUn^itcs. All of the known specimens of this species show it to be an evolute form with compressed whorls, higher than wide, and with a flattened venter. The inner whorls bear slight radial ribs which are strongest near the mnbilical shoulder and decrease down the flank; the weak ribs can be observed throughout the phragmocone. On the living chamber, the pattern of orna- mentation is more irregular and is more like irregular bundled growth lines. The full details of the suture were not available to Frebold, but on one of his specimens— Ammonites sp. indet. (Frebold, 1929a: pi. 1, fig. 13; PI. 26, figs. 3, 4 of this report) — it has been possible to develop the suture (Fig. 28D). The suture bears two lateral lobes that are clearly denticulated, and a smooth auxiliary lobe on the umbilical wall. The highlv crvstalline nature of the phrag
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