海蕾是一类已灭绝的棘皮动物。多为梨形，有茎和腕羽，萼部较小。底板（冠部与茎的连接板）3块，音叉状的辐板（底板之上与口面之间的骨骼）5块。海蕾纲约有90属左右，生活在志留纪至二叠纪，超过一半的属发现于石炭纪早期。

海蕾纲（Blastoidea）在分类上属于海百合亚门（Crinozoa），也有学者将海蕾纲（Blastoidea）、拟海蕾纲（Parablastoidea）、海林檎纲（Cystoidea）及始海百合纲（Eocrinoidea）4纲划归为一个亚门，称为海蕾亚门（Blastozoa）。

Blastoids (class Blastoidea) are an extinct type of stemmed echinoderm. Often called sea buds, blastoid fossils look like small hickory nuts. They first appear, along with many other echinoderm classes, in the Ordovician period, and reached their greatest diversity in the Mississippian subperiod of the Carboniferous period. However, blastoids may have originated in the Cambrian. Blastoids persisted until their extinction at the end of Permian, about 250 million years ago. Although never as diverse as their contemporary relatives, the crinoids, blastoids are common fossils, especially in many Mississippian-age rocks.