glass-crab

from The Century Dictionary.

• noun A crab of the spurious genus Phyllosoma, or of the spurious order Phyllosomata—that is, any young shrimp of either of the families Palinuridæ and Scyllaridæ. These larvæ are as thin as paper, flat and transparent, and have no resemblance to the adult.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) The larval state (Phyllosoma) of the genus Palinurus and allied genera. It is remarkable for its strange outlines, thinness, and transparency. See phyllosoma.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The larval state (Phyllosoma) of the genus Palinurus and allied genera, remarkable for its strange thinness and transparency.