already referred to, its resemblances are especially striking, viz. to Semionotus Bergeri, Ag.[1], of the German Keuper, and Lepidotus minor of the English Purbeck.
Fishes of this genus occur in the Triassic strata of North America; it is also said to have been found in the Lower Permian schists of Autun, in France[2].
VI. Type of Palæoniscus glaphyrus, Ag. (? Genus Acentrophorus, Traquair). I have not seen the type specimen of this rare species from the English Marl Slate; but, to judge from the figures given in the 'Poissons Fossiles'[3] and in King's 'Permian Fossils'[4], the conclusion seems unavoidable that it is neither a Palæoniscus nor a member of the family of Palæoniscidæ. Certain suspicious details occur in Agassiz's description—for instance, that the mouth is "très-petite," also that the fulcra "diffèrent de ceux des autres espèces en ce qu'il sont plus allongés et moins serrés contre le bord des nageoires." This latter condition is very distinctly represented in the figure of the species, in which we also miss the prominent heterocercy characteristic of the Palæoniscidæ: in fact the entire aspect of the fish, as there delineated, is eminently suggestive of its affinity to the three little species from Fulwell Hill, Durham, described by Mr. Kirkby as Palæoniscus varians, Abbsii, and altus[5], but whose reference to that genus is certainly erroneous. Until, however, the type specimen is reexamined, it would be unsafe to pronounce as to the generic identity of P. glaphyrus with these last-mentioned forms: at least one marked distinction is found in the denticulation of the scales in the former, a difference which may possibly be only of specific importance.
But as regards the non-palæoniscoid nature of the Fulwell-Hill fishes there cannot be the smallest doubt: and although these species are not Agassizian, it may not be altogether out of place here to devote a little more attention to them than a mere passing reference. That they are not Palæonisci has been already pointed out by Dr. Lütken, of Copenhagen, in the following terms, "But already in the Dyas we find, alongside of a preponderating number of heterocercal forms, a few half-homocercal ones." And in a footnote appended to the same passage he says, "as, for example, Palæoniscus Abbsii, varians, and altus from the English Permian formation, which should be expelled from the genus Palæoniscus (like the North-American Triassic species, also previously referred to Palæoniscus, which are now called Ischypteras, Catopterus,
- ↑ Poissons Fossiles, vol. ii. pt. 1, p. 224–227. Strüver in Zeitschr. der deutschen geol. Gesellsch. xvi. 1864, pp. 303–330, pl. xiii.
- ↑ The statement that "at Autun, in France, we find the genus Ischypterus accompanying the true Palæonisci" is made by Sir Charles Lyell (Quart. Journ. Geol. Soc. iii. 1847, p. 278); but Sir Philip Grey-Egerton, three years later, states that he is not cognizant of any species of the genus being found there (ibid. vi. 1850, p. 8).
- ↑ Atlas, vol. ii. tab. 10 c. figs. 1 and 2.
- ↑ Pl. xxii. fig. 3.
- ↑ Ann. & Mag. Nat. Hist. (3) ix. 1862, pp. 267–269, also in Quart. Journ. Geol. Soc. xxi. 1865. pp. 345–358.
