XXV. _CHRYSOTRICHACEAE_ This family now, according to Hue[1047], includes two genera, _Crocynia_ and _Chrysothrix_. In both there is a thallus of interlaced hyphae with Protococcaceous algae scattered through it or in groups. The structure is thus homoiomerous, and Hue has suggested for it a new series, “Intertextae.” The only British species, _Crocynia lanuginosa_, first placed by Nylander[1048] in _Amphiloma_ and later transferred by him to _Leproloma_[1049], has a soft crustaceous lobate thallus, furfuraceous on the surface; no fructification has been found. A West Indian species, _C. gossypina_, has discoid apothecia with a thalline margin. There is only one species of _Chrysothrix_, _Ch. nolitangere_, which forms small clumps or tufts on the spines of Cactus in Chili. The structure is somewhat similar to that of _Crocynia_. Spores colourless, simple 1. Crocynia Nyl. Spores colourless, 2-3-septate 2. *Chrysothrix Mont. XXVI. _THELOTREMACEAE_ A tropical or subtropical family of which the leading characteristic is the deeply sunk disc of the apothecium: it has a proper hyphal margin, and, round that, an overarching thalline margin. The apothecia occur singly, or they are united in a kind of pseudostroma: in _Tremotylium_ several grow together, while in _Polystroma_ each new apothecium develops as an outgrowth from the thalline margin of the one already formed, so that an upright, branching succession of fruits is built up. It is a very unusual type of lichen fructification, with one species, _P. Ferdinandezii_, found in Spain and in Guiana. The thallus in all the genera is crustaceous with an amorphous (decomposed) cortex; or it is non-corticate. The algal cells are _Trentepohlia_ except in _Phyllophthalmaria_, an epiphyllous genus associated with the alga _Phycopeltis_. In _Polystroma_ the alga is unknown. Only one genus is represented in the British Isles. Apothecia growing singly. Thallus with _Trentepohlia_ gonidia. Paraphyses numerous, unbranched, free. Spores colourless. Spores elongate, 2- or multi-septate 1. *Ocellularia Spreng. Spores muriform 2. Thelotrema Ach. Spores brown. Spores elongate, septate 3. *Phaeotrema Müll.-Arg. Spores muriform 4. *Leptotrema Mont. Paraphyses scanty, branched. Spores muriform, brown 5. *Gyrostomum Fr. Thallus with _Phycopeltis_ gonidia 6. *Phyllophthalmaria A. Zahlbr. Apothecia in pseudostromata. Apothecia united in tubercles 7. *Tremotylium Nyl. Apothecia united by the margins 8. *Polystroma Clem. XXVII. _DIPLOSCHISTACEAE_