It has a single hairy leaf and up to three large, mainly white flowers with very long, drooping lateral sepals and petals, and a white broad labellum with relatively short labellum teeth.

There are four or more rows of pale red calli in the centre of the labellum.

[2][3][4][5] Caladenia longicauda was first formally described by John Lindley in 1840 and the description was published in A Sketch of the Vegetation of the Swan River Colony.

[3] Merritt's white spider orchid mainly occurs between Augusta, Margaret River and Nannup in the Jarrah Forest and Warren biogeographic regions where it grows in jarrah forest.

merrittii is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.