Venus, 1714

Reading William Derham's Astro-Theology, or a Demonstration of the Being and attributes of God from a survey of the heavens (1714), I came across this intriguing aside:

Viewing Venus with Mr. Huygens’s glass divers nights, when near her perigee, and much horned, I thought I saw anfractus or roughnesses on the concave part of the enlightened edge (such as we see in the new moon), which I have represented as nearly as I could in fig.12. [4]

The Google-books copy doesn't include any figures, alas; but I wonder about this. The obvious thing would be to say: Derham was mistaken; for we now know that Venus's cloud cover is so thick as not to permit any glimpse of any feature that might accord with what Derham saw. But if it wasn't a mistake, and Derham reported accurately what he saw, then what might it have been? Perhaps an asteroid or cometary strike upon Venus at the start of the eighteenth-century, that temporarily disturbed the cloud-cover?