From The Collaborative International Dictionary of English v.0.48 [gcide]:
Chelonia \Che*lo"ni*a\ (k[-e]*l[=o]"n[i^]*[.a]), n. pl. [NL.,
fr. Gr. chelw`nh a tortoise.] (Zool.)
An order of reptiles, including the tortoises and turtles,
peculiar in having a part of the vertebr[ae], ribs, and
sternum united with the dermal plates so as to form a firm
shell. The jaws are covered by a horny beak. See Reptilia;
also, Illust. in Appendix.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
Chelonia
n 1: green turtles [syn: Chelonia, genus Chelonia]
2: tortoises and turtles [syn: Chelonia, order Chelonia,
Testudinata, order Testudinata, Testudines, {order
Testudines}]