New dental and skeletal material referable to Palaeochiropteryx tupaiodon from the Middle Eocene locality of
Messel (G.F.R.) is studied, which provides additions to the previously gained knowledge of this european genus. Dental specimens from Geiseltal (G.D.R.), also of Middle Eocene age, allow us to analyze Cecilionycteria prisca. Some of these are separated to establish a new genus, Matthesia, and two new species, M. germanica and M. ? insolita. 

The revision of the Lutetian chiropterans from Messel, first described by Revilliod in 1917, is based on the anatomy of the teeth and the skeleton.  A figuration or refiguration of thematerial utilized accompanies the new description, which goes beyond that of the original monograph.
The study shows a certain variability of the dental structure within the genera Palaeochiropteryx Revilliod and Archaeonycteris Revilliod,  as well as a general resemblance of the two forms. The morphology of the teeth permits, however, the verification of the validity of the different species: Palaeochiropteryx tupaiodon Revilliod, P. spiegeli Revilliod, Archaeonycterís trigonodon Revilliod, and Archaeonycteris revilliodi, n. sp.
Some differences of the skeletal and dental anatomy tend to indicate a stage of evolution less advanced for the genus Archaeonycteris.
The comparison of the chiropterans of Messel with the principal groups of living chiropterans, as well as with different Eocene fossíls (notably Cecílionycteris Heller and Icaronycteris Jepsen) leads to a more precise idea of the anatomy of primitive chiropterans. This comparison also permits the proposition that the oid forms so far described by integrated in a superfamily, the Palaeochiropterygoidea and allows   a general phylogenetic hypothesis to be advanced for the order Chiroptera.