The ravine has a series of waterfalls, cascades and boulder chokes, and some good base-rich rock at its upper end. Previous records are of Harpalejeunea molleri and Sphenolobopsis pearsonii: I refound the former but missed the latter. More tantalising was a 19th century record of Paraleptodontium recurvifolium, which has old records from 10+ N Wales sites but recent ones from just 2 or 3 and it's possible that some/many/all of these result from misidentification of the related Oxystegus daldinianus (until recently considered an extreme form of Trichostomum tenuirostre). There's a lot of O. dalinianus in the ravine, but no sign of Paraleptodontium.
As well as Harpalejeunea, which was abundant over ca 8x1m of a base-rich rockface and also occurred on a boulder downstream, there was one rock covered with Drepanolejeunea hamatifolia (a new site) and another with a few tufts of Colura calyptrifolia (also a new site). Whereas Colura is now commonplace on trees in southern Wales, it remains very rare on rocks in its traditional ravine habitat.
Highlight of the day was spotting a patch of Bartramia halleriana about 3m up the ravine side, below which were a few fallen tufts growing among Hyocomium. This is the first SH64 record of this Nationally Scarce moss.