Twelve elements (Cu, Ni, Mn, Ti, Si, Cr, Sr, V, Ba, Ag, Pb, and Mo), not previously reported from the genus Velella, were found in the ash of V. lata; zirconium was also searched for but was not found. Cu, Ni, Mn, Ti, Mg, Ca, and Al were determined quantitatively. The concentration of trace elements in the whole animal and in five different tissues of V. lata was determined in specimens ranging from 14.4 to 84.6 mm in length. The Mg:Ca ratio in Velella is lower than that in sea water but. higher than that in Scyphozoa. Presumably this is due to concentration of magnesium in the chlorophyll of commensal zooxanthellae.