MIDDLE CAMBRIAN FOSSILS FROM TIZI-NTICHKA, THE HIGH ATLAS, MOROCCO .1. INTRODUCTION AND TRILOBITES

New finds of the trilobites Cobboldites tichkaensis Geyer, 1988, Pseud ocobboldia pulchra (Hupe, 1953), Protolenus (Protolenus) densigranulat us Geyer, 1990, Latoucheia (Latoucheia) tichkaensis Hupe, 1953, and Ac anthomicmacca neltneri Hupe, 1953, from the basal Middle Cambrian near the peak of Tizi n'Tichka in the central High Atlas, Morocco, supplem ent the known morphology of these species; the trilobites Acanthomicma cca new species, Oreisator tichkaensis new genus and species, and ''Pa rasolenopleura'' sp. from that locality are new. Acanthomicmacca neltn eri is the first-species of the genus and family that is described and figured in detail in terms of morphologic plasticity and ontogeny; Or eisator tichkaensis is the first ptychopariacean trilobite formally de scribed and based on material from Africa. Trilobites and other fossil s from the locality suggest a strong affinity to other Mediterranean a nd to Avalonian faunas, which is well supported by helcionelloid and h yolith genera.