The Collaborative International Dictionary of English v.0.48:

Halisauria \Hal`i*sau"ri*a\ (h[a^]l`[i^]*s[add]"r[i^]*[.a]), n.
   pl. [NL., fr. Gr. "a`ls, "alo`s, sea + say^ros.] (Paleon.)
   The Enaliosauria.
   [1913 Webster]