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  1. Cart-rut2_amber-louise_burberry Cart-rut shell opening by AL Burberry
  2. Cart-rut3_amber-louise_burberry Distinct parallel ridges on shell by AL Burberry
  3. Img_3693__c_gillies-cropped Cart-rut shell attached to rocks underwater by C Gillies

Cart-rut Shell

Dicathais orbita


  • Largest intertidal marine snails 
  • Obvious parallel ridges or circular bumps 
  • Usually white to light brown in colour 
  • The final whirl is small, about half the size of the maximum height. 
  • Size:  up to 80mm

What to Observe

Search area for 30 minutes and record under the following categories:

  • Abundant - found easily with little searching
  • Frequent - found with minimal searching
  • Rare -  only 1 or 2 individuals found with intensive searching
  • Not found - not present during search

ClimateWatch Science Advisor

Cart-rut, like all marine snails (molluscs), are under increasing stress due to ocean acidification which can weaken their calcium carbonate shells and reduce body condition. This makes them more prone to disease, predation and low reproduction. Increasing water temperature as a result of climate change will likely affect their abundance and cause a southward shift in their distribution.

When To Look

Throughout the year

Where To Look

  • Common on rocky shores, from low to mid tide levels. Usually found rock pools, crevices and wet areas. 
  • Barrow Is WA, SA, TAS, VIC, NSW up to Southern QLD. 


Davey, K. (1998). A Photographic Guide to Seashore Life of Australia. New Holland Publishers Australia Pty Ltd.


Edger, GJ. (2008). Australian Marine Life. The Plants and Animals of Temperate Waters [2nd Ed]. New Holland Publishers Australia Pty Ltd.


  1. Search Species

  1. What Else?

    Cart-rut snails are the only large marine snail (50-80cm long) that can be found living on rocky platforms and can be distinguished from other large marine snails by being almost as wide as they are long. Other large marine snails, such as whelks, are likely to be washed in from the sea and found as dead shells and will be at least twice as long as they are wide.  

  1. Did You Know?

    Cart-rut shell get their name from the appearance of the parallel grooves that resemble the wheel ruts (grooves) left behind from a horse and carriage, which was the standard mode of transport at the time this species was first identified.

    Cart-ruts are carnivorous molluscs that like to feed on barnacles and mussels.

    Can also be found in New Zealand.

    A study in WA found that the largest specimens were around 20 years old.