Article: Holaspid variation in the solenopleurid trilobite Parasolenopleura gregaria (Billings, 1865) from the Cambrian of Newfoundland

The Cambrian trilobite originally described as Bathyurus gregarius by Billings in 1865 is revised in the light of a new collection from what is judged to be its type locality in the Big Gully Marl Member of the Chamberlain's Brook Formation on the Cape St. Mary's Peninsula of south-east Newfoundland. Here assigned to Parasolenopleura gregaria, it is regarded as the senior synonym of Parasolenopleura cristata (Linnarsson, 1877) in the Swedish Paradoxides (Eccaparadoxides) insularis and P. (Plutonides) pinus zones, and Parasolenopleura lemdadensis Geyer, 1998 in the Moroccan Ornamentaspis frequens-Kymataspis arenosa zonal boundary beds. Among its features, important details of the relationships of the genal caeca to the eye and cephalic borders are given, as well as illustrations of the significant range of biotic and abiotic morphological variation in holaspid growth stages of the cephalon that will have some bearing on the revision of the Solenopleuridae.