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Vol. 36(2), 2001

Figs 1-16 Shells: 1-3) Aylacostoma exoplicata from Tucurui, Para, 1-2) fronUii vicw of holotypc and a parafy pe, 3) dorsal vicw of a youngcr paratype, scalę - 5 mm; 4-6) Aylacostoma ci from Jamari Rivcr, Roraima, thrce spoci mens in frontal vicw (hololype and Iwo paralypes), sealc = 5 mm; 7-8) Aylacostoma tenuilabris from Avare, Sao Paulo, 7) frontal and 8) dorsal vicw, scalc = 5 mm; 9-10) Aielanoides fuberculafus (Muller), Eurasian spccies found in Pantanal, Mato Grosso do Su), 9) dorsal, 10) frontal vicw, scalc = 5 mm; 11) Doryssa macapa from Araguari Rivcr, Amapa, frontól view, sealc - 10 mm; 12) Doryssa ipupiara (holotypc) from Apui, Roraima, frontal view; 13) Doryssa oanwersa (Lca) from Roraima; 14) Doryssa atra (Bruguierc) from Frcnch Guyana, frontal view, scalc = 5 mm; 15-16) Pachychilus sp from Chiapas, Mcxico, 15) frontal, 16) dorsal vicw, scalc = 5 mm.