specious

Seemingly well-reasoned, plausible or true, but actually fallacious.

This idea that we must see through what we have started is specious, however good it may sound.

now to the discourse itself, voluble enough, and full of sentence, but that, for the most part, either specious rather than solid, or to his cause nothing pertinent.

Employing fallacious but deceptively plausible arguments; deceitful.

With early virtues plant your breaſt, / The ſpecious arts of vice deteſt.

But a third cause of the delusion is, that the Church of Rome has become more specious and deceitful than before the Reformation.

Having an attractive appearance intended to generate a favorable response; deceptively attractive.

And could any thing be more ſpecious, or more equal, than that fair diſtribution of power and profit, which men called the NEW MODEL?

[T]he success of Trajan, however transient, was rapid and specious. The degenerate Parthians, broken by intestine discord, fled before his arms.

Beautiful, pleasing to look at.

Alternative form of speciose (“rich in species”).

Coelorinchus is the most specious genus of macrourids with 122 species at the time of writing and more yet to be described.