Author: Blainville, 1816
Remarks:
Whitley (1934), followed by Fowler (1941) proposed that the genus Cetorhinus should be replaced by Halsydrus, which was based on the carcass of a 'sea monster' washed ashore in the Orkney Islands and eventually identified as a basking shark. According to Bland and Swinney (1978), Halsydrus as originally proposed was apparently a nomen nudum, separately proposed from descriptions of the Orkney 'monster', and does not comprise a senior synonym of Cetorhinus. The genus Tetroras (and its variant Tetnoras) is hard to identify from Rafinesque's (1809) generic description, with his claim that Tetroras has four gill openings being plainly erroneous. The description of Tetroras angiova, the only species in the genus, does indeed suggest a basking shark in certain details "denti in forma di raspa... ha gli occhi piccolissimi, e le aperture delle branchie bastantemente larghe.". However, even if more evidence was available to prove that T. angiova actually was a basking shark, the substitution of Tetroras for Cetorhinus would not serve the stability of zoological nomenclature due to virtually universal usage of Cetorhinus for the genus of the basking shark at present