The angularity of this bivalved shell made it immediately noticeable on the sandy beach at Cairns. It is called a Twisted Ark because of the strange configuration of the shell which is strongly twisted with a sharp ridge from the top to the margin. The Latin name is Trisidos tortuosa (Linnaeus), formerly Arca tortuosa. It varies from 60 – 100 mm in length and occurs on the Australian coast from the Northern Territory to Queensland.
Reference
Jansen, P. (1996) Common Seashells of Coastal Northern Queensland, privately published in Townsville, Australia, November 1996. ISBN 0 646 29824 0.
Jessica's Nature Blog 
It’s like a mini modern sculpture – nature being a bit contemporary perhaps?
LikeLike
Yes, it is rather like an abstract sculptural form. I wonder why it evolved that particular shape and what kind of competitive edge the design would give the species in life?
LikeLike
It’s beautiful. I love seashells and can’t believe that I don’t live near the beach! I don’t think three hours away qualifies as near.
LikeLike
Thank you. Maybe, living where you do, you appreciate what the seashore has to offer even more when you do get an opportunity to visit.
LikeLike