The Collaborative International Dictionary of English v.0.48:

Gymnosomata \Gym`no*so"ma*ta\ (j[i^]m"n[-o]*s[=o]"m[.a]*t[.a] or
   j[i^]m"n[-o]*s[o^]m"[.a]*t[.a]), n. pl. [NL., fr. Gr. gymno`s
   naked + sw^ma, sw`matos, the body.] (Zool.)
   One of the orders of Pteropoda. They have no shell.
   [1913 Webster]