About Echinostrephus aciculatus A.Agassiz, 1863
Echinostrephus aciculatus A.Agassiz, 1863 is a species of regular sea urchin with a canonical body shape. Its test (hard internal skeleton) is mostly spherical, and displays pentaradial symmetry, with the mouth positioned at the center of the oral face and the anus on the aboral face. Its spines are thin, sharp, and average in length. The diameter of the test ranges from 2 to 4 centimetres, or 0.79 to 1.57 inches. Spine color is highly variable: spines are most often brown-purple, but may also be any shade of purple, brown, black, grey, or off-white. Spines located on the oral face can be cream-colored with brown-purple rings, though these rings are rarely visible. The test itself ranges in color from black to light brown, and the base of the spines often bears sharply contrasting color rings. The apical disk at the top of the test is dark, lacks spines, and forms a clearly visible shape at the apex of the test.
