Spores 1- or more-septate 4. Allarthonia Nyl. Spores muriform 5. *Allarthothelium Wain. Thallus with _Phycopeltis_ gonidia. Spores elongate 1- or more-septate 6. *Arthoniopsis Müll.-Arg. XIX. _GRAPHIDACEAE_ Thallus crustaceous, inconspicuous, partly immersed, mainly growing on bark but occasionally on dead wood or stone. Algal cells chiefly _Trentepohlia_, very rarely _Palmella_ or _Phycopeltis_ (epiphyllous). Apothecia (lirellae) carbonaceous more or less linear, opening by a narrow slit with a well-developed proper margin except in _Gymnographa_, a monotypic Australian genus. In two genera, the fruit is of a compound nature, several parallel discs occurring in one lirella: these are _Ptychographa_ (on bark in Scotland) and _Diplogramma_ (Australia), both are monotypic. They must not be confused with _Graphis elegans_ and allied species in which the sterile carbonaceous margin is furrowed. Two tropical genera associated with _Phycopeltis_ are epiphyllous. Graphidaceae are among the oldest recorded lichens, attention having been drawn to them since early times by the resemblance of the lirellae on the bark of trees to hieroglyphic writing. Thallus with _Palmella_ gonidia. Apothecia single. Hypothecium dark-brown. Spores simple 1. Lithographa Nyl. Hypothecium colourless or brownish. Spores colourless. Spores simple 2. Xylographa Fries. Spores elongate 3-8-septate 3. *Aulaxina Fée. Spores brown. Spores 1-septate 4. Encephalographa Massal. Spores pluri-septate, then muriform 5. *Xyloschistes Wain. Apothecia compound. Spores simple, colourless 6. Ptychographa Nyl. Spores pluri-septate, colourless 7. *Diplogramma Müll.-Arg. Thallus with _Trentepohlia_ gonidia. Spores elongate 1-multi-septate, the cells longer than wide. Spores brown. Spores 1-(rarely more)-septate 8. Melaspilea Nyl. Spores 3-septate (apothecia rudimentary) 9. *Gymnographa Müll.-Arg. Spores colourless. Spores acicular, coiled (many in the ascus) 10. *Spirographa A. Zahlbr. Spores fusiform, straight 11. Opegrapha Humb. Spores muriform. Spores elongate, central cells finally muriform 12. *Dictyographa Müll.-Arg.