About Thylacodes arenarius (Linnaeus, 1758)
Thylacodes arenarius (Linnaeus, 1758) has irregular shells that grow to a length of approximately 100 to 200 millimetres (3.9 to 7.9 inches). The round aperture of its shell reaches a diameter of 11 to 15 millimetres (0.43 to 0.59 inches). The inner surface of the shell is smooth and shiny. These shells are cemented to hard surfaces, and resemble the calcareous tubes built by some marine worms, such as polychaetes in the family Serpulidae. The visible portion of the mollusk's body is red, marked with cream-colored patterns. The foot of this species is atrophied, and has lost its ability to move. This species is distributed in the Eastern Basin of the Mediterranean Sea, and in European coastal waters of the North Atlantic Ocean.
