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Show 887.] ON THE TELEOSTEAN GENUS RHACOLEPIS. 535 4. On the Fossil Teleostean Genus Rhacolepis, Agass. By A. S M I T H W O O D W A R D , F.Z.S., F.G.S., of the British Museum (Natural History). [Received June 7, 1887.] (Plates XLVI. & XLVII.) Among the numerous fossil fishes named and briefly noticed by Agassiz during the preparation of his great work ' Reeherches sur les Poissons Fossiles,' but reserved for adequate description in the contemplated supplements which unfortunately never appeared, are some interesting specimens from the north of Brazil, displaying the characters of an extinct generic type, mentioned under the name of Rhacolepis. Of these the British Museum now contains an extensive series, enriched especially by the recent acquisition of the Egerton and Enniskillen collections; and as materials are thus provided for a tolerably complete elucidation of the ancient fish they represent, the present seems a favourable opportunity for completing the original diagnoses. The majority of the fossils were actually examined by Agassiz himself, and several bear his MS. labels, so that it is possible to recognize the various species he intended to establish. And a careful study of the whole series has lately revealed some novel facts in regard to the affinities of the genus, which appear to have hitherto escaped observation, and render it of considerable interest to the zoologist. The fossil fishes in question, together with four or five other genera, are discovered in calcareous nodules, of concretionary origin, scattered upon the hill-sides in the neighbourhood of Barra do Jardim, Serra de Araripe, North Brazil, and the first published allusion to them appears to occur in the record of Spix and Martius's travels at the beginning of the present century 1. About 1840 many specimens were collected by Mr. George Gardner, of Glasgow, who submitted them to Agassiz, and briefly described the circumstances under which they were met with 2; and these, probably, form the greater part of the Museum collection at the present time. Still others were brought under Agassiz's notice by M M . F. Chabrillac and Elie de Beaumont, and formed the subject of a lengthy report published in the ' Comptes Rendus' for 1844 3. Nearly thirty years later, Professor C. F. Hartt added further remarks upon the geological evidence as to the age of the nodules themselves 4; and 1 J. B. von Spix and C. F. von Martius, ' Reise in Brasilien,' 1823-31, Atlas, pl. 22. fig. 5. 2 Gr. Gardner, " Geological Notes made during a Journey from the Coast into the Interior of the Province of Ceara in the North of Brazil," Edinb. New Phil. Journ. vol. xxx. 1841, pp. 75-82.-L. Agassiz, " O n the Fossil Fishes found by Mr. Gardner," ibid. p. 83. 3 L Agassiz, " Sur quelques poissons fossiles du Bresil," Comptes Rendus, TOI. xviii. (1844), pp. 1007-1015. 4 C. F. Hartt, ' Geology and Physical Geography of Brazil (Thayer Expedition),' 1870, chaps, xiii., xiv. passim. |