TABLE 1 in Taxonomic significance of test morphology in the echinoid genera Diadema Gray, 1825 and Echinothrix Peters, 1853 (Echinodermata)

TABLE 1. — Test measurements, proportions and features for Diadema antillarum Philippi, 1845 and D. ascensionis Mortensen, 1909. Abbreviation: SD, standard deviation.
D. antillarumD. ascensionisOrigin of specimens examinedBarbados, Gulf of Mexico,Ascension and St HelenaJamaica, N Panama, Puerto Rico,islands (South Atlantic)Virgin IslandsTest colourblackblack (red tinge)Test shapehemisphericalhemisphericalTest distinctionsambulacra slightly raised aborallyambulacra slightly raisedaborallyIridophore pattern (interambulacra)blue lines (faint)blue lines (faint)Iridophore pattern (apical system)blue ring (faint)blue ring (faint)Iridophore pattern (genital plate)blue arch (faint)blue arch (faint)Mean horizontal test diameter (SD)85 mm (5.1 mm)70 mm (5.2 mm)Mean vertical test diameter (SD)45 mm (3.7 mm)40 mm (3.4 mm)Maximum horizontal test diameter observed105 mm84 mmMaximum vertical test diameter observed50 mm46 mmMarkings on test (median area ofday: no marking; night: faint whiteday: no marking; night: faintinterambulacra)spotwhite spotMarkings on naked test (median area ofnonenoneinterambulacra)Markings on naked test (genital plate)arch-shaped (fades with age)arch-shaped (fades with age)Number of tubercles on genital plate2-4 small tubercles0-2 small tuberclesHeight to width (at widest point) ratio of0.76:10.71:1genital plateDiameter of gonopore (% of genital plate29%31%height)Form of apical systemhemicyclichemicyclicForm of periproct (distinguishing features)small black, no ring or plateletssmall black, no ring or plateletsApical system (% of horizontal test diameter)18-22%20-26%Periproct (% of horizontal test diameter)10-14%12-18%Peristome (% of horizontal test diameter)45-50%40-50%Ambulacra % of interambulacra (at ambitus)25-33%25-30%Tubercle structureperforate and crenulateperforate and crenulateNumber of median series of tubercles on21interambulacraRudimentary tube feet present on thenonoperistomeBuccal tube feet present5 pairs5 pairsSpines present on the buccal platesnonoNumber of specimens examined5028