. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. REVISION OF LATE VALANGINIAN CEPHALOPODA 333. Fig. 184. Olcostephanus {Olcostephanus) sayni gerec- seiensis (Somogyi). The holotype (after Somogyi 1916). x 1. bullae. Parabolae are lacking. This species may be distinguished from the present material by its more numerous umbilical bullae and finer, denser secondary ribs. Somogyi (1916) distinguished O. sayni gerecseiensis (Fig. 184) on the basis of its flexuous secondary ribbing. Olcostephanus scissus (Baumberger) (Fig. 185) is a species which has lon
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. REVISION OF LATE VALANGINIAN CEPHALOPODA 333. Fig. 184. Olcostephanus {Olcostephanus) sayni gerec- seiensis (Somogyi). The holotype (after Somogyi 1916). x 1. bullae. Parabolae are lacking. This species may be distinguished from the present material by its more numerous umbilical bullae and finer, denser secondary ribs. Somogyi (1916) distinguished O. sayni gerecseiensis (Fig. 184) on the basis of its flexuous secondary ribbing. Olcostephanus scissus (Baumberger) (Fig. 185) is a species which has long been confused with and O. sayni, from which it is readily distinguish- able by its fewer umbilical bullae. It is a compressed form with a narrow umbilicus and sloping umbilical walls ornamented with 14 radial primaries. These termi- nate in bullae giving rise to generally 4, fine, prorsiradiate secondaries which frequently bifurcate high up on the flank. There are frequent intercalated ribs between bundles and parabolae are apparently lacking. This species is very close to O. astierianus from which it seems to differ only in possessing bullate umbilical tubercles and in the frequent bifurcation of the secondary ribs in O. scissus. O. astieriformis has more numerous bullae and does not show bifurcation of the secondary ribs. Olcostephanus subfilosus Spath (Fig. 186) is based upon a nucleus which bears parabolae and displays about 16 umbilical bullae from which arise numerous fine, prorsiradiate secondaries, with intercalated ribs between bundles. A topotype example (Fig. 187) in the Oxford University Museum, OUM-K1207, shows a rather narrow, deep, crater-like umbilicus with steep, convex walls and an evenly rounded umbilical shoulder. Primary ribs begin at, or close to, the umbilical seam and curve backwards (rursiradiate) to about 20 bullae on the umbilical shoulder of the outer whorl. Each bulla gives rise to 4-6 prorsi- radiate secondaries with 1-2 intercalated ri
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
