To whatever cause the absence of mosses may be best attributed, it is a fact that should not be too strongly emphasised in discussions on plant-evolution. _Muscites._ This comprehensive genus may be defined as follows:— Stem filiform, simple or branched, bearing small sessile leaves, with a delicate lamina, without veins or with a single median vein, arranged in a spiral manner on the stem. _Muscites_[473] is one of those convenient generic designations which limited knowledge and incomplete data render necessary in palaeontology. Fossil plants which in their general habit bear a sufficiently striking resemblance to recent mosses, may be included under this generic name. [Illustration: FIG. 51. _Muscites polytrichaceus_ Ren. and Zeill. (after Renault and Zeiller).] 1. _Muscites polytrichaceus_ Renault and Zeiller. In this species the stems are about 3–4 cm. long and 1·3 m. broad, usually simple, but sometimes giving off a few branches, and marked externally by very delicate longitudinal grooves. The leaves are alternate, closely arranged, lanceolate, with an acute apex, gradually narrowed towards the base, 1–2 mm. long, traversed by a single median vein. One of the French specimens, on which the species was founded[474], is shown in fig. 51, and the form of the leaves is more clearly seen in the small enlarged piece of stem. The authors of the species point out that the tufted habit of the specimens, their small size, and the membranous character of the leaves, all point to the Musci as the Class to which the plant should be referred in spite of the absence of reproductive organs. Among recent mosses, the genus _Rhizogonium_,—one of the _Mniaceae_,—and _Polytrichum_ are spoken of as offering a close resemblance to the fossil form. The type-specimen was found in the Coal-Measures of Commentry, and is now in the Museum of the École des Mines in Paris; the figure given by MM. Renault and Zeiller faithfully represents the appearance of the plant. • • • • • It has been suggested[475] that some small twigs figured by Lesquereux[476] from the Coal-Measures of North America as _Lycopodites Meeki_ Lesq., may possibly be mosses. The specimens do not appear to be at all convincing, and cannot well be included as probable representatives of Palaeozoic Musci. _Lycopodites Meeki_ Lesq. bears a close resemblance to the recent _Selaginella Oregana_ shown in fig. 48, C.