Cladonia mitis. Treated by some as a subspecies of Cladonia arbuscula. In many ways, it is halfway between arbuscula and portentosa. It differs from C. arbuscula in having groups of branches all pointing the same way, and is fequently more robust towards the base. It also tends to be more blue. However, especially where the two species grow together, intermediates are observed. To be certain of it, especially as it is so rare, it should be given a TLC (thin layer chromatography) test to see what lichen acids it contains. This photograph was taken in one of two main  sites for it on shingle in north-east Scotland.