In 1965 I suggested that C. nematosum might be identical with C. wightii. At that time I could not see the type specimen of Meteorium nematosum C. Müll., the basionym of C. nematosum. Meteorium nematosum was based on a specimen from Pegu, Burma (S. Kurz 2695), but the holotype specimen seems to have been lost. Recently I examined a specimen labelled: "2695 Pegu, Mide forest 28/12/70, Herb. Hampe 1881" (BM). This label bore ''Pilotrichum nematosum CM " in handwriting, probably that of C. Müller. The plants in this collection are characterized in the following description (also see Fig. 9).
Secondary stems (or branches) short, simple, occasionally with few branches, arcuate, obtuse or attenuate (± flagelliform), and ca. 4 mm thick. Leaves dense, wide- or erect-spreading, concave, widely ovate and acute or shortly acuminate; the tips sometimes semi-twisted, and serrulate and the bases largely auriculate; costae slender, extending 2/3 the leaf length. Median laminal cells linear, 60-85 x 5-6 µm and thin-walled; the cells at the auriculate base linear, arranged in a spiral manner.
I here designate the above specimen as the neotype of M. nematosum C. Müll. In the original description C. Müller compared this species with Pilotrichella wightii (a homotypic synonym of C. wightii), and I consider M . nematosum to be conspecific with C. wightii. In 1976 Gangulee reported M . nematosum C. Müll. under the genus Pterobryopsis and illustrated it. His illustration of leaves shows the characters of M. nematosum (Gangulee, 1977, fig. 612), but the sporophytes are not from this species, because the elongate setae are different from those of the genus Calyptothecium (sensu Heischer, 1906-1908; Noguchi, 1965). I examined the specimen of Pterobryopsis nematosa (C. Müll.) Dix. (cal), on which Gangulee's figures were based, and found that his specimen is a mixture of C. wightii (in small amount) and Stereophyllum sp. (with several sporophytes).
Calyptothecium dixonii Gang.—This was described by Gangulee based on a specimen from Charduar, Assam, India (N. L. Bor 207) (Fig. 7). This specimen was determined by Dixon as Calyptothecium sp. (bm), and is accompanied with a label reading as follows: "Bry. E. Levier, Mus. Hep. Indiae Orientalis. Mysore, India Merid. leg. Khan, Sept. 1903. Broth. 5925 as Calyptothecium mysorense Broth, nova spec, in litt. 1903." From the above description I infer that Dixon considered the plants to be C. mysorense but he did not publish the name. The following is a description based on Bor 207.
The plants dark green, partially yellowish-green and slightly glossy. Secondary stems reach 3 cm in length, by 4 mm in thickness, usually simple, occasionally with few innovated branches, and often arcuate and obtuse at apex. Leaves widely spreading when dry, widely ovate, scarcely acute or shortly acuminate at apex, and distinctly auriculate at base. Median laminal cells linear or sublinear, 60-65 x 4-5 µm, thin-walled. Fusiform gemmae present.
I have examined the type specimen of C. dixonii, and could not find any stable differences from the characters of C. wightii.