Northern cup coral

Astrangia poculata

Family Rhizangiidae - corals

Colonial polyps arranged in clumps of cup-like structures (corallites); live polyps are translucent to brown, with numerous tentacles, appear fuzzy looking; skeleton yellowish to white; corallites are tightly packed, circular, can be up to 10 mm (0.4 in) but usually not more than 5 mm (0.2 in) in diameter; inside cups are skeletal radiating plates (septa), septa are irregularly beaded, usually 24 in number; cups may be touching each other or slightly separated; skeletal material between cups (coenosteum) present, cups raise above coenosteum with definite walls; small ridges on outside of cup (called costae, are extensions of the inside septa) with granulated margins; encrusting (grows on other structures), non-reef forming.
Similar Species
The southern cup coral, A. solitaria may be clumped but the cups grow separately (coenosteum between cups rarely present). Cups are small (=<6 mm or <1/3 in) on extended columns. Their septa are usually 36 in number (up to 48).
Gulf and bay, attaches to hard substrates, jetties, pilings, oyster shell
Maximum Size
corallites up to 1 cm (0.4 in) in diameter, usually 5 mm (0.2 in) or less
Other Common Names
northern star coral, false coral
Previous Scientific Names
A. danae, A. astreiformis
This is the coral commonly seen on oyster shells in the bays.