Carboniferous Palcæonisci all belong to types essentially distinct from that of P. Freieslebeni.
II. Type of Palæoniscus Duvernoyi, Ag. (Genus Amblypterus, Ag.). This includes fishes with mostly rather deep bodies arcuated in front of the dorsal fin, which is situated rather further back than in the true Palæonisci; the median fins are large; the tail large and powerful; the scales usually smooth; the suspensorium only slightly oblique; the teeth probably very minute. There must be included (besides the Agassizian species P. Duvernoyi, wratislaviensis, and lepidurus), the P. dimidiatus, elongatus, tenuicauda, gibbus, and opisthopterus of Troschel, the P. Gelberti of Goldfuss, the P. decorus, arcuatus, and Beaumonti of Egerton, and, I think, also the P. Rohanni, caudatus, obliquus, Reussii, and luridus of Heckel. P. minutus, angustus, Voltzii, and Blainvillei of Agassiz seem to be allied forms, though the latter especially may possibly be the type of still another genus.
Between these species and the smooth-scaled Amblypteri of Saarbrücken and Lebach I can, as already stated, see no tangible grounds of generic distinction, though in some (e.g. P. decorus) the fins are rather smaller and their fulcra more prominent. But the slight obliquity of the suspensorium, the general form of the body, the position of the fins, and the aspect of the squamation are similar in all. As regards the scales, they are mostly smooth, or show only slight concentric lines; in some, however (e.g. P. Gelberti, P. Beaumonti), those of the front of the flank display a certain amount of ornamentation. They are certainly not Palæonisci in the strict sense of the term: and until at least their cranial structure and dentition are more fully elucidated, they are better classed with Amblypterus than with any other genus. Giebel had, indeed, previously proposed to transfer P. Duvernoyi to Amblypterus, but, unfortunately, on the untenable ground that the fulcra were absent in it except on the upper lobe of the tail.
All these species are from strata similar in age to the beds at Saarbrücken &c., in which the typical Amblypteri occur, and which are now referred by continental geologists to the Lower Permian (unteres Rothliegendes). Even the fish-bearing schists of Autun, characterized by Palæoniscus Blainvillei, have ceased to be reckoned as appertaining to the 'Terrain houiller.'
III. Type of P. striolatus, Ag. (Genus Elonichthys, Giebel). Here are included P. striolatus, Robisoni, and Egertoni, fishes with large median fins, sculptured scales, powerful tail, very oblique suspensorium, and, as regards the dentition, possessed of a row of distinct conical laniaries internal to a series of smaller teeth. It is difficult to conceive why Agassiz placed these species in the genus Palæoniscus, while at the same time he described, as has been already shown, certain closely allied forms from the Wardie shales as Amblypteri. They are all, in my opinion, referable to the genus Elonichthys of Giebel. (See also under type of Amblypterus nemopterus, p. 553.)
IV. Type of Palæoniscus ornatissimus, Ag. (Genus Rhadinichthys,
