In a series of papers I have described numerous species of Hyaloscyphaceae from Europe (Dennis, 1949), tropical America (Dennis, 1954, I958b, I96o), Australia (Dennis, 1958a) and New Zealand (Dennis, 1961). In the following compilation will be found descriptions and figures of the remaining species of which authentic material has been deposited at Kew under the generic names Dasyscyphus, Erinella, Lachnella, Lachnellula, Solenopezia and Trichopeziza. An attempt has also been made to borrow and describe the type collections of as many as possible of the other species listed by Seaver (1951), after his treatment of Lachnella, as 'Doubtful and excluded Species', with the exception of those preserved at New York State Museum and not accessible to students. A number of other type collections of Hyaloscyphaceae borrowed from various European herbaria have also been included. For convenience of reference the species are arranged in alphabetical order of their specific epithets. In recent years and especially in a recent summary of the HyaloscyphaceaeLachneae (Dennis, 1962), I have laid stress on the importance of lanceolate paraphyses in delimiting genera of Helotiales. This holds good for almost all species in which the paraphyses are well developed, i.e. those in which they are at least as long as or overtop the asci. There are, however, a few Hyaloscyphaceae in which these organs are very slender, feebly developed and scanty or even almost absent, but in which the other characters, especially those of the hairs, are those of Dasyscyphus. Because well developed paraphyses are a feature of the 'Discomycetous' hymenium throughout so many genera and families it seems likely that apothecia in which they are feebly developed are t6 be regarded as derivative rather than primitive forms. It also appears doubtful if any close relationship exists between these Da.yscyphuslike species with feebly developed paraphyses. On the contrary there sometimes appears to be a closer relationship between individual species with filiform paraphyses and others with lanceolate paraphyses on a similar substrate than there is between members of the first-named group. Such apparent pairs of species are, for example,. Dasyscyphus diminutus and D. fugiens; Dasyscyphus fuscescens and D. acerinus; Dasyscyphus dumorum and D. misellus; where in each case the first named has normal lanceolate paraphyses and the second has them scanty and filiform. It is not claimed that the first species in each pair stands in a directly ancestral relationship to the second. Nevertheless an apparent relationship does exist and I therefore feel it premature to propose distinct genera such as Clavidisculum Kirschstein or Discocistella Svr6ek (1962) to accommodate these few Dasyscyphi with anomalous paraphyses. The name Dasyscyphus dates from S. F. Gray 1821 but from the time of Fuckel 1870 until very recent years the spelling of the name was changed to Dasyscypha. In citations printed below the spelling originally adopted by S. F. Gray has been restored, without comment in most cases, where a name in Dasyscyphus is adopted for current use.