Fig. 4 in Early ontogeny and palaeoecology of the Mid-Miocene rissoid gastropods of the Central Paratethys

Fig. 4. Four species of Rissoa Desmarest, 1814. A. Rissoa turricula Eichwald, 1853. Specimen (collection A. Papp, NHMW 2002z0030/0001) from the Early Sarmatian of Waldhof/Styria (A1). Protoconch of the same specimen in lateral view (A2). The protoconch is terminated by a thickened rim, reflecting the thickened apertural margin of the veliger ready for metamorphosis. B. Rissoa parva (Da Costa, 1778). Specimen (NHMW 2002z0030/0002), Recent, from the Northern Adriatic Sea (B1). Protoconch of the same specimen in lateral view (B2). The protoconch is terminated by a prominent slightly sinuous, thickened rim. C. Rissoa acuticosta (Sacco, 1895). Specimen (NHMW 2002z0030/0003) from the Badenian of Steinebrunn, Lower Austria (C1). Apical and lateral view of the protoconch of the same specimen (C2, C3). The protoconch is terminated by sinuous, closely spaced, thickened growth lines. D. Rissoa clotho Hörnes, 1856. Specimen (NHMW 2002z0030/0004) from the Badenian of Steinebrunn, Lower Austria (D1). Protoconch of the same specimen in lateral view (D2). The protoconch is terminated by an indistinct, very fine thickened rim on the shell. Regular closely spaced growth lines indicate the onset of the teleoconch.