. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. Fig. 57. Olcostephanus {Olcostephanus) sakalavensis (Besairie). A hypotype in the collections of the University of Paris, from Ambiky, Madagascar. x 1. Olcostephanus sakalavensis (Besairie) (Figs 56-57) is a strongly inflated macroconch species with a very depressed whorl section. The steep umbilical walls are ornamented with about 12 rursiradiate primaries per half whorl which terminate in bullae on the umbilical shoulder. From these arise bundles of 4-6, fine, prorsiradiate secondaries with interca
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. Fig. 57. Olcostephanus {Olcostephanus) sakalavensis (Besairie). A hypotype in the collections of the University of Paris, from Ambiky, Madagascar. x 1. Olcostephanus sakalavensis (Besairie) (Figs 56-57) is a strongly inflated macroconch species with a very depressed whorl section. The steep umbilical walls are ornamented with about 12 rursiradiate primaries per half whorl which terminate in bullae on the umbilical shoulder. From these arise bundles of 4-6, fine, prorsiradiate secondaries with intercalated ribs between bundles, so that there are 36 secondaries across the venter per 7 umbilical bullae on the outer whorl of the holotype. Parabolae are lacking at all growth stages. Modern revision of the European material will probably show that O. sakalavensis is a synonym of O. densicostatus. Olcostephanus filifer (Imlay) (Fig. 58) was created for a large, strongly inflated macroconch with a broadly convex venter. The umbilicus of this species is narrow and deep, with vertical walls ornamented by 20 weak, rursi- radiate primaries which terminate in rather weak tubercles at the umbilical shoulder. Each tubercle gives rise to 4-5 fine, prorsiradiate secondary ribs with 1-2 intercalated ribs between bundles. Parabolae are lacking. This species was said to differ from O. densico status'm its finer ribbing and more numerous umbilical tubercles, but the differences are slight and probably do not warrant specific separation. Olcostephanus filifer is certainly a synonym of O. sakalavensis. Olcostephanus spathi (Besairie) (Fig. 59) is based upon the inner whorls of a macroconch. It is a moderately inflated species with a semilunate, depressed whorl section. The umbilical walls are strongly convex and ornamented with 25 rursiradiate primaries which terminate in rather small umbilical bullae. From these arise bundles of slightly prorsiradiate, almost rectiradiate, second- aries whose c
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
