Therefore, in order to separate further these two species, and in addition to the characters mentioned above, the following differences should be considered : in T. axenos the excretory syncytia are elliptical, whereas in T.mertoni n.sp. they are elongate, and wider in the area surrounding the excretory pore; in T. axenos, the intestinal septa are very conspicuous, and T. mertoni n. sp. has only two; in T.axenos there are two sphincters in the female portion of the atrium, but in T. mertoni N.sp. there is only one.Differences were also found between the eggs of both species, given that in T. axenos the eggs have a short, subterminal ornamentation, and opercular plates perpendicular to the longitudinal axis of the egg