Figs 10A, 32A, 36D
Specimen FMNH-P30425 from Profilstranda section, adjacent to Hinlopenstretet, Spitsbergen, bed PO 131, 128 m above base of Olenidsletta Member, V 2b trilobite zone, Blackhillsian, Floian.
The specimen is a 20 mm long orthoconic fragment of a phragmocone with a ca 3 mm long basal part of the body chamber. The conch cross section is slightly elliptically depressed with a width of 9.5–10.8 mm and a height of 8.7–9.2 mm (rW = 1.13; angle of expansion of conch height 9°).
The ornamentation consists of widely rounded annulations that form a shallow sinus at the prosiphuncular side of the conch and have a distance of ca 3 mm and an amplitude of ca 0.5 mm; the valley and ridges of the annulations are widely rounded. Fine details of the conch surface, which potentially exist, such as growth lines or striae, are not preserved. Roughly one annulation occurs per one chamber.
The chambers have a distance of 3–3.5 mm (ca three chambers occur at a distance similar to conch height, rCL = 0.33). The siphuncle is nearly marginal and has a diameter of 3.7 at the adapical end, and 3.9 mm at the adoral end (0.42 of conch height). The connecting ring is thick and consists of slightly concave segments. The shape and length of the septal necks is difficult to interpret because of the poor preservation of the specimen, but they appear to be short orthochoanitic. No cameral or endosiphuncular deposits occur.
This is an annulated orthocone with a large siphuncle, larger than the range given for Catoraphiceras in the diagnosis of Hook & Flower (1977). The assignment of the fragment to Catoraphiceras is justified because all other characters are in agreement with the diagnosis of this genus and there is no other annulated orthocone with a marginal, empty siphuncle with slightly concave segments and short septal necks. Among the species of Catoraphiceras with depressed conch cross section C. colon (White, 1875) and C. resseri Ulrich et al., 1944 are most similar to specimen FMNH-P30425; the former mainly differs in having an annulation of only 2 annuli per distance similar to corresponding conch height, the latter differs in having a smaller siphuncle with rSD = 0.35. The siphuncle of Catoraphiceras sp. is also larger than the siphuncle of C. ibexense Hook & Flower, 1977 (rSD = 0.24). The single, relatively poorly preserved fragment available from the Olenidsletta Member, however, does not allow for the erection of a new species. The erection of a new species based on this fragmentary specimen is also not possible, because several species are known to contain endosiphuncular deposits, which may or may not exist in more apical, non-preserved, portions of specimen FMNH-P30425.