Fig. 29 in Early-Middle Ordovician cephalopods from Ny Friesland, Spitsbergen - a pelagic fauna with Laurentian affinities

Fig. 29. Median sections of phragmocones of Bactroceras Holm, 1898. A, C–D. Bactroceras fluvii sp. nov., from Profilbekken river basin, locality PR-phosphatic. A. Specimen FMNH-P30159, with adapical siphuncular segment, taphonomically slightly distorted.B. Bactroceras boliviensis Aubrechtová, 2015, FMNH-P30176 from bed PO 131, extreme apical part. C–D. Specimen FMNH-P30177, holotype. C. Details of the protoconch. D. Apical part with transition toward juvenile growth stages; note the slightly expanded siphuncular segments. Scale bars: A = 5 mm; B–C = 1 mm; D = 2 mm.