Decry means to denounce or disparage. Descry means (1) to see in the distance or (2) to discern with the eye. Both verbs come from the Old French descrier, meaning to call or cry out. In modern English, though, they have have developed distinct meanings.
Examples
These writers use decry well:
We decry rote memorisation merely because it is old-fashioned. But aren’t today’s cut-and-paste PowerPoint presentations even dumber? [Times Higher Education]
While some hardcore fans of Austen’s novels will continue to decry this line of books for altering classic literature, they have to admit that it’s gotten better this time around. [Book Addict Diary]
And these writers use descry well:
Visitors to the platform will be able to look south and descry their counterparts at the top of the fast-rising Shard … [Londonist]
She creates landscapes and still-lifes in simple compositions, in whose powerful lines and forms we descry flowers, clouds, butterflies, mountains, stars and a horizon. [Paperblog]

