Agastograptus, a synonym of Plectograptus (Retiolitidae, Graptolithina) Author Kozłowska-Dawidziuk, Anna text Acta Palaeontologica Polonica 2002 2002-12-31 47 3 459 467 journal article 300550 10.5281/zenodo.13173828 3dbd2041-0711-4651-bdf5-2d771a498f0c 1732-2421 13173828 Cometograptus nevadensis ( Berry and Murphy, 1975 ) Fig. 3D . Retiolites nevadensis n. sp. ; Berry and Murphy 1975: 100 , pl.15: 5, 6. Agastograptus nevadensis (Berry and Murphy) ; Obut and Zaslavskaya 1983: 107 . Spinograptus nevadensis (Berry and Murphy) ; Lenz 1993: 23 , pl. 19: 1–6, pl. 20: 1–7. Cometograptus nevadensis (Berry and Murphy) ; Lenz and Kozłowska−Dawidziuk 2001: 18 , pl. 11: 1–6. Diagnosis .—See Kozłowska−Dawidziuk 2001. Discussion .— Cometograptus nevadensis is recognized as a species of the Cometograptus group restricted to the Cyrtograptus lundgreni Biozone (Kozłowska−Dawidziuk 2001) . The crucial difference between Plectograptus and Cometograptus is in the position of seams on the ancora sleeve lists, which may indicate the mode of list secretion, whether from the outside or from the inside (Bates and Kirk personal communication 1999). In Cometograptus seams on lists face out, the opposite of Plectograptus . There are also differences in arrangement of the ventral wall lists, presence of transverse rods, and development of apertural processes as a spine−like genicular hoods with seams, probably signifying some kind of membrane between them. Occurrence .— Cometograptus nevadensis occurs in two places: Arctic Canada and Central Nevada, North America, both in Cyrtograptus lundgreni Biozone.