As shown above, SN71 is shared between Glamorgan and Carmarthenshire, the former much the poorer cousin of the latter in terms of bryophyte habitats. However, a tetrad with <60 species is always a challenge and this afternoon I visited the very small bit of SN71C in Glamorgan (i.e. the northern part of the coal storage site south of the Afon Aman shown below), taking it to 70 species. Note the MapMate vc41 boundary is rather crude and shows boundaries in some squares that do not exist (e.g. on the map above it looks like part of SN71H is in Glamorgan, but it isn't and I have corrected some of the squares on the tetrad map after checking the boundary thoroughly using 'Grab a Grid Reference Duo' shown below. Note, you can use the 'toggle vice county' filter below the satellite map to view the appropriate boundary and zoom right in. There are still four more Glamorgan boundary squares to be done in SN71 and two in SN81. A quick look in the Carms Bryo-flora shows the Carmarthenshire squares have all been visited, a couple of which are in the 61-90 species category, so 60-70 seems a realistic target for the remaining Glamorgan squares in this hectad.
The bridge abutments and adjacent walls were of limited interest though Gymnostomum aeruginosum was abundant.
Finally, as is so often the case, the grass (or moss) always looks greener on the other side of the fence (or river), but unfortunately my wellies weren't tall enough to venture across to this part of Carms, but an easy site to access, so maybe worth a check when the river is lower...