Catalogue of the fossil fishes in the British Museum (Natural History) .. . of Genera. A. Paired spines between pectoral and pelvicfins insignificant or minute or absent; median pair of spines between pectorals Diphcanthus (p. 23). DIPLACANTHID^. 23 B. Paired spines between pectoral and pelvic finswell dorsal fin-spine not exceeding the posterior in length Climatius (p. 28). Anterior dorsal fin-spine much exceeding the jrior in length Parexus (p. 33). Genus DIPLACANTHUS, Agassiz.[Poiss. Foss. V. G. E. 1844, pp. 34, 40.]Syn. Rhadinacanthus, R. H. Traqnair, Geol.
Catalogue of the fossil fishes in the British Museum (Natural History) .. . of Genera. A. Paired spines between pectoral and pelvicfins insignificant or minute or absent; median pair of spines between pectorals Diphcanthus (p. 23). DIPLACANTHID^. 23 B. Paired spines between pectoral and pelvic finswell dorsal fin-spine not exceeding the posterior in length Climatius (p. 28). Anterior dorsal fin-spine much exceeding the jrior in length Parexus (p. 33). Genus DIPLACANTHUS, Agassiz.[Poiss. Foss. V. G. E. 1844, pp. 34, 40.]Syn. Rhadinacanthus, R. H. Traqnair, Geol. Mag. [3] vol. v. 1888, p. 512. Body fusiform, probably not much laterally compressed. Teethminute or absent; orbit with ring of four circumorbital dermalplates. Pectoral fins large, and a median pair of stout spines fixedbetween these to the basal pterygia; a pair of free spines situatedventrally between the pectoral and pelvic fins. The pectoral fins in this genus are somewhat difficult of interpre-tation, but the accompanying woodcut (fig. 3) seems to represent Fig. Pectoral arch and fins of Diplacanthus striatus, Ag.—b, basal cartilage ;cl. clavicle; , infraclavicle; m, median spine; s, fin-spine. the arrangement of the spines and pectoral arch in the type is usually the case in crushed specimens, the fin-spines are exhi-bited from the dorsal aspect, and the ascending limb of the pectoralarch is bent forwards and exposed from the inner side. The greaterportion of the pectoral arch consists of a pair of vertically elongatedelements (cl), each having a straight rod-like axis, filled with calcitein the fossil, and thus originally either hollow or occupied by uncal-cified tissue; behind this axis there is a thin laminar expansionof bone, diminishing upwards, and apparently extending downwardsand inwards to form an inferior limb. The pair of large bones doesnot meet in the median line below, but is separated by a muchsmaller pair of bony laminae (), unit
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Keywords: ., bookauthorbritishmuseumnaturalh, bookcentury1800, bookdecade1880
