Trona stercoraria (Linnaeus, 1758) by diver at night, low tide in seaweed at 3 meters, M’bour, Senegal
Trona stercoraria (Linnaeus, 1758) dwarf. by diver on rocks at 10 meters, Gulf of Guinae, Limbe, Cameroon

Trona stercoraria (Linnaeus, 1758) is a popular cowrie among collectors due to its extreme variability in size, shape, color and even pattern. Its common name the Rat Cowry or Droppings Cowry. Certain populations have overcastings that make for bizarre specimens which may look as if they were infected by disease (and possibly they are). These are common in some locations.
Even with all the variation stercoraria is easily recognized and can’t be confused with any other cypraea. Its coloration could be considered drab (mousy, hence the name Rat). It is certainly not flashy. Typical specimens have a mocha colored base with dark brown chiseled teeth. The dorsum is similar in color and covered with blurred brown blotches. Some specimens are light, others dark in color. Scarce specimens have a largely clear dorsum, others with an irregular pattern while the occasional one has the blotches fused to almost sold and even scarcer almost black. The margins are calloused and both extremities are rostrate. Sizes run from extreme dwarfs of 1″ to giants of about 3.75”. The majority fall between 2 and 2.5″. While typically rhomboid, sone specimens are oval.
There are populations with an extreme hump that were named Trona stercoraria rattus (Lamarck, 1810). Linnaeus call the dwarfs “minima”. Even with all the variation the vast majority have the patterns and shape of the two offered here.
Trona stercoraria is a West African cowry with a restricted range below the Bulge of Africa. Most specimens come from the Gulf of Guinea. It is fairly common in this area and lives in a variety of shallow water habitats.
The two shells were donated by Richard Kent and were obtained from European dealers. Average sized specimens retail for $20-25, dwarfs though much scarcer somewhat less. Large ones go for over $30. Giants and unusual specimens can be found on eBay from $60 to over $300. In fact there is one very dark 95mm specimen with blueish borders listed for sale at $520!