Subsequent taxonomic splits have restricted the name to the populations in the Southland and Otago regions in New Zealand's South Island.

[2] Chilton's original material was collected on Mihiwaka, a hill near Port Chalmers, Otago.

[2] In November 2018 the Department of Conservation classified C. rivertonensis as "Nationally Critical" under the New Zealand Threat Classification System.

[4] The species was judged as meeting the criteria for Nationally Critical threat status as a result of it occupying only in one location, the total area of which is less than 1 hectare.

Whereas all the other species occur in fresh water, C. minuta was collected under kelp on a beach on Campbell Island.