engastrius

engastrius

 [en-gas´tre-us]
a double fetus in which one fetus is contained within the abdomen of the other.

en·gas·tri·us

(en-gas'trē-ŭs),
Unequal conjoined twins in which the smaller parasite is wholly or partly within the abdomen of the larger autosite.
[G. en, in, + gastēr, belly]

engastrius

a double monster in which one fetus is contained within the abdomen of the other.