Scarcely differing from the preceding family except in the gonidia which are Protococcaceous algae. The thallus is crustaceous and non-corticate. The apothecia have a double margin but the outer thalline margin is less overarching than in Thelotremaceae. The spores in the two genera are somewhat peculiar: in _Conotrema_ they are exceedingly long and divided by parallel septa into thirty to forty small cells; in _Diploschistes_ (_Urceolaria_) they are large, muriform and brown. _Conotrema_ contains two corticolous species; _Diploschistes_ about thirty species mostly saxicolous. Both genera are represented in the British Isles. Spores elongate, multi-septate, colourless 1. Conotrema Tuck. Spores muriform, brown 2. Diploschistes Norm. XXVIII. _ECTOLECHIACEAE_ A family of tropical epiphyllous lichens that are associated with Protococcaceous gonidia. The thallus is primitive in character, mostly a weft of hyphae with intermingled algal cells, described as homoiomerous. The apothecia are without a thalline margin, and with a scarcely developed proper margin: their affinity is with the Lecideaceae, though in two genera, _Lecaniella_ and _Arthotheliopsis_, there are gonidia below the hypothecium, a character of Lecanoraceae. The genera are nearly all monotypic; in _Sporopodium_ has been included _Lecidea phyllocharis_ Wainio (Sect. _Gonothecium_), which is distinguished by hymenial gonidia. Apothecia at first covered by a “veil.” Spores elongate, colourless, septate 1. *Asterothyrium Müll.-Arg. Apothecia uncovered from the first. Gonidia not present below the hypothecium. Paraphyses unbranched, free. Spores muriform 2. *Lopadiopsis Wain. Paraphyses branched. Spores 1-septate 3. *Actinoplaca Müll.-Arg. Spores elongate, multi-septate 4. *Tapellaria Müll.-Arg. Spores muriform 5. *Sporopodium Mont. Gonidia present below the hypothecium. Spores elongate, 2-septate 6. *Lecaniella Wain. Spores muriform 7. *Arthotheliopsis Wain. XXIX. _GYALECTACEAE_ The algal cells in this family are filamentous; either Myxophyceae (_Scytonema_) or Chlorophyceae (_Trentepohlia_ or _Phyllactidium_). The thallus is crustaceous, and in some cases homoiomerous, as in _Petractis_, where the alga, _Scytonema_, penetrates the substratum as deeply as the hyphae. _Monophiale_, a tropical genus, possesses two kinds of gonidia: the species that grow on bark or mosses are associated with _Trentepohlia_; others that have invaded the surface of leathery evergreen leaves resemble most epiphyllous lichens in being associated with the leaf alga _Phyllactidium_ (_Phycopeltis_). Some species of _Trentepohlia_ exhale when moist an odour of violets. This scent is retained in at least one genus, _Jonaspis_.