THE ANNALS AND MAGAZINE OF NATURAL HISTORY. [FOURTH SERIES.] No. 88. APRIL 1875. XXX. — On the Structure and Systematic Position of the Genus Cheirolepis. By E. H. Traquair, M.D., F.G.S., Keeper of the Natural-History Collections in the Edin-burgh Museum of Science and Art. [Plate XVII.] This very interesting genus of Devonian fishes was originally described by the late Prof. Agassiz, in the second volume of his ' Poissons Fossiles,' p. 178, and was then included by him in his family of '^ Lepidoides." The first step towards the breaking-up of that heterogeneous assemblage was taken by Agassiz himself, in the course of the publication of the same great work, when he constituted the family of Acanthodidje for the genera Cheir acanthus^ Acanfhodes, and Cheirolepis] and this classification was retained in his special work on the Fossil Fishes of the Old Red Sandstone, The founder of fossil ichthyology seems, however, to have had but a slight and not very correct conception of the structure of the fishes with which he associated Cheirolepis, as may be seen both from his restored figures and his remark that, as the bones which he had been able to distinguish in Cheirolepis, '' such as the frontal, humerus, temporal, have the same structure as in ordinary osseous fishes," one may conclude " that the Acanthodians in general had a complete osseous system, and not merely a chorda doi-salis as in the Coccostei and other fishes of the same epoch"*. Subsequent investigations into * Poissons Fossiles du vieux Gres Rouge, p. 44. Ann. d:Mag. N. Hist. Ser. 4. Vol. xv. 17
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