Habitat: Turtle grass beds and sand fields bordering turtle grass beds. Distribution: Texas, South Carolina to Barbados, Caribbean, Panama. Natural History Notes: The fat sea biscuit lives on the surface of the sand and frequently covers the upper surface of its test with fragments of turtle grass, shell, and rock. It uses oral surface accessory podia with terminal suckers to ingest dead turtle grass or dead algae. Feeding activity is nocturnal. A single individual is capable of grinding 5.5 kg /year of coarse sand to fine sand, and may play a major role in the production of fine sediment on reefs. In Panama, C. rosaceus has an annual reproductive cycle; spawning occurs during the rainy season, at random with respect to the lunar cycle. The egg and larva contain a considerable amount of yolk. Metamorphosis occurs after 5-7 days at an average temperature of 27 degrees C. Depth: 0-285m, most common at shallow depths Characteristics: The fat sea biscuit is relatively long (up to 200 mm) and elongate. It is dark brown, and inflated, with a strongly convex upper surface and a concave lower (oral) surface. The test is covered with short spines. It is not uncommon to come upon dead tests, as the naked test is thick and strong.