The morphology of the osteocranium and the Weberian apparatus of 14 representatives of Tachysuridae (= Ariidae) has been described and compared. It has been shown that these features are characteristic of the family Tachysuridae (= Ariidae) and can also distinguish the genera and the species of this family. A key to the intergeneric and interspecific characters has been provided. A few characters of morphological interest have been recorded. It has been shown that the erection of different genera for some species of the genus Tachysurus (=Arius) by Munro (1955) is arbitrary and lacks support from morphology. The features of the oesteocranium and the Weberian apparatus support the fact that Tachysuridae are not primitive siluroids; they are at least more specialized than Siluridae, Plotosidae, and Bagridae. The advanced features of Tachysuridae are described. The morphological relationship of the superficial bone and its associated trough-like bony structure with the swim-bladder show that these bony formations develop from the tunica externa of the latter.