_Coprinus radiatus_ (Fries) S. F. Gray is smaller in stature and also differs in spore-size (11-14 × 6-7 µm). _C. pseudoradiatus_ Kühner & Josserand is minute and has even smaller spores (7-9 × 4-5 µm). The dung-heap ink-cap has long been used by scientists in genetic studies, usually under the name of _C. lagopus_ (Fries) Fries. However, this latter species, although similar, grows only on woodland detritus; it has narrower spores. The dung-heap ink-cap may be referred to in other books as _C. fimetarius_ Fries or _C. macrorhizus_ (Fries) Rea and whilst _cinereus_ means grey referring to the colour, _fimetarius_ means dung--from the habitat, and _macrorhizus_ refers to the long rooting base found in some specimens. _Illustrations_: LH 137; NB 41¹⁰; WD 81⁴. The genus _Coprinus_--or Ink-caps The genus _Coprinus_ is easily recognised from all other agarics by the structure and development of the fruit-body. In the field, most species of the genus can be recognised by the gradual conversion of the gills, and often the cap tissue into a black liquid resembling ink--hence the name inky-caps. The conversion of the gills to an inky mass is called autodigestion and the process is complete within a few hours; this mechanism enables spores to be dispersed immediately they have ripened. Unlike other agarics the spores are not shot off into the spaces between the gills, but directly into the air. The gills are parallel-sided in _Coprinus_ and not wedge-shaped as in more normal agarics, and in order to achieve spore dispersal the gills must disintegrate; Coprini are very specialised. _Coprinus_ is a large genus with over seventy members in the British Isles, many of which are strictly dung-loving. It is impossible to give more than one example in full here, for although many of the large species can be recognised on sight the smaller ones require the aid of a microscope. The interested student must therefore refer to more advanced texts, but in order to demonstrate the diversity of the Coprini and how they are classified the following key to the sections of _Coprinus_ will be found useful. 1. Cap naked of any veil fragments, either smooth or covered in minute hairs 2 Cap covered when young by powdery or hairy veil, particles of which either may persist on the cap until maturity or may disappear quickly 3 2. Cap completely naked--group Nudi, e.g. _C. miser_ (Karsten) Karsten Cap with hairs giving it a frosted appearance--group Setulosi, e.g. _C. ephemerus_ (Fries) Fries, _C. pellucidus_ Karsten and _C. bisporus_ J. Lange 3. Veil on the cap composed under the microscope of rounded cells giving the cap a floccose powdery appearance--group Vestiti, e.g. _C. patouillardii_ Quélet, _C. niveus_ (Fries) Fries and _C. ephemeroides_ (Fries) Fries