ABSTRACT

Spiriferina? (Lepismatina?) stracheyi (Salter) has been the subject of special attention in the Himalayas because of its abundance and its very restricted vertical but great lateral distribution. Only a single and somewhat dubious occurrence has been reported from elsewhere. The species described here is from three localities in northeastern British Columbia and two from west-central Alberta. These occurrences are restricted to a thin, apparently isochronous horizon which correlates in age with the Himalayan "S." stracheyi horizon as accurately as determinable.

The thin Durgaites dieneri zone with "S." stracheyi of the Spiti limestone in the west-central Himalayas is correlated with the Paraceratites binodosus zone of the Alpine standard succession, and is of early late Anisian age. The species occurs within the Toad formation of the British Columbia Foothills and at the base of the Whitehorse formation in the Spray River group of the Alberta Foothills and Front Ranges, respectively: the horizon represents the base of the late Anisian "Beyrichites-Gymnotoceras-Parapopanoceras fauna" in both formations.

The "S." stracheyi horizon of the Canadian Rocky Mountains usually is marked by structures of slight reworking and/or shell concentration, and disconformably overlies Lower Triassic beds with the hiatus increasing from north to south.

The species is redescribed and its affinities discussed. It displays an extraordinarily great range of variation in all essential morphological characters which is very similar to the Himalayan form. The statistics will be discussed separately.