The chert member of the San Hipólito Formation contains a diversified, fairly well-preserved, Late Triassic radiolarian assemblage which includes 25 new species, 8 new genera, 1 new subfamily, and 1 new family. Numerous other taxa are figured but not described, either due to their poor state of preservation or to rareness. The member is divided into a lower capnodoce Zone (late Karnian to late middle Norian) and an upper Pantanellium silberlingi Zone (late middle Norian to late Norian). Investigations now in progress indicate that the Capnodoce Zone is widespread in the western part of the Cordilleran region. In addition to the occurrence of this Zone in Baja California, it is known from the Rattlesnake Creek terrane of the Klamath Mountains of California, from the Brisbois Formation and the Rail Cabin Argillite (Suplee-Izee area) of eastern Oregon, and from the Cache Creek Group of British Columbia. The P. silberlingi Zone appears to be present in the Kunga Formation of the Queen Charlotte Islands.