The most highly evolved family of the subseries, as regards the thallus. Algal cells Protococcaceae. In _Tholurna_, a small lichen endemic in Scandinavia, there is a double thallus: one of horizontal much-divided squamules, the other swollen, upright, terminating in the capitulum. The fruit is lateral in _Calycidium_, a squamulose form from New Zealand, and in _Pleurocybe_ from Madagascar, with stiff strap-shaped fronds. All the genera are monotypic except _Sphaerophorus_, of which genus ten species are recorded, some of them with a world-wide distribution. The spores are brown and simple or 1-septate. Thallus squamulose and upright 1. *Tholurna Norm. Thallus wholly squamulose 2. *Calycidium Stirton. Thallus fruticose. Fronds hollow in the centre 3. *Pleurocybe Müll.-Arg. Fronds not hollow. Fruit without a thalline margin 4. *Acroscyphus Lév. Fruit inclosed in the tip of the fronds 5. Sphaerophorus Pers. SUBSERIES 2. =Graphidineae= In this subseries are included five families that differ rather widely from each other both in thallus and apothecia; the latter are more or less carbonaceous and mostly with a proper margin only. Families and genera are widely distributed, though most abundant in warm regions. Algal cells mostly _Trentepohlia_. A comprehensive study of the apothecia of this series by Bioret[1044] gives some interesting results in regard to the paraphyses: in _Arthonia_ they are irregular in direction and much-branched; in _Opegrapha_, the paraphyses are vertical and parallel with more regular branching; _Stigmatidium_ (_Enterographa_) resembles _Opegrapha_ in this respect as does also _Platygrapha_, a genus of Lecanactidaceae, while in _Graphis_ the paraphyses are vertical, unbranched and free; _Melaspilea_ paraphyses are somewhat similar to those of _Graphis_. XVIII. _ARTHONIACEAE_ The thallus of Arthoniaceae is corticolous with few exceptions and is very inconspicuous, being largely embedded in the substratum. The apothecia (ardellae) are round, irregular or stellate, without any margin, the hymenium being protected by the dense branching of the paraphyses at the tips. _Arthonia_ is abundant everywhere. The species of the other genera belong mostly to tropical or subtropical countries. _Arthoniopsis_ is similar to _Arthonia_ in the character of the fruits, but the gonidium is a _Phycopeltis_, and it is only found on leaves. _Synarthonia_ with peculiar stromatoid fructification is monotypic; it occurs in Costa Rica. Thallus with _Trentepohlia_ gonidia. Apothecia scattered. Spores elongate 1- or pluri-septate 1. Arthonia Ach. Spores muriform 2. Arthothelium Massal. Apothecia stromatoid. Spores elongate, multi-septate 3. *Synarthonia Müll.-Arg. Thallus with _Palmella_ gonidia.