Histionotus Angularis, was first described and figured by the late Sir Philip de M. Grey Egerton, Bart., F.R.S., in Decade viii. of the Memoirs of the Geological Survey, 1853. The uninterrupted dorsal fin, extending from near the occiput to the tail, suggested the generic name of Histionotus, and in this feature it reresembles Ophiopsis. It has the characters also of other genera, for instance, Pholidophorus in its scales, Semionotus in the shape of its body, and Lepidotus in the shape of its head. Sir Philip Egerton, misled by the imperfect preservation of the posterior end of his specimen, thought the caudal-fin to be also similar to that of Lepidotus.