. Chimæroid fishes and their development. Fishes; Chimaeridae. ROSTRUM, , FINS. 129 nasal septum (usually its base) is probably represented in the element which Schauinsland has figured as sp in his plate xvii, fios. 124, 126. However, in the Chima?roid the rostral supports (/-'and r") later developed into long and separately jointed elements. Quite doubtful, on the other hand, are the homo- logues of the paired dorsal elements in the selachian rostrum, those figured, c. g., by Kitchen Parker in Trans. Zool. Soc, vol. x, plate xxxviii, fig. i, as btr; they are possibly th
. Chimæroid fishes and their development. Fishes; Chimaeridae. ROSTRUM, , FINS. 129 nasal septum (usually its base) is probably represented in the element which Schauinsland has figured as sp in his plate xvii, fios. 124, 126. However, in the Chima?roid the rostral supports (/-'and r") later developed into long and separately jointed elements. Quite doubtful, on the other hand, are the homo- logues of the paired dorsal elements in the selachian rostrum, those figured, c. g., by Kitchen Parker in Trans. Zool. Soc, vol. x, plate xxxviii, fig. i, as btr; they are possibly the homologues of Schauinsland's elements ,s- in the figures quoted. Equally doubtful is the more dorsal azygous element (Schauinsland's rV v. the present fig. 11 i), which folds forward and becomes a main support of the produced snout in Callorhvnchus; it certainly finds no homologue in sharks, and in view of the history of the frontal clasping organ in Chimseroids {v. figs. 132-137) I am inclined to interpret it as an element, /. r., a fin support, transjiosed from a hinder position,* a view which is the less difficult to accept when one considers the metamorphosis to which the head roof has been subjected by the precocious growth of the M BH B Figs. 1 10 and 'V b'H B'B-'B-'B'B^ Skull and branchial arches of Shark and Chimaeroid compared. i?I-i?'>, Branchial arches: i?//, basihyal: 6^^, basis trabecularum (Kitchen Parker) : C, copula : C/?, ceralobranchial: AV>', Epibranchial; ///>', hypobranchial; /'. " anteriormosl lip cartilage " (Kitchen Parker); 3A mandible ; -P-S, pharyngobranchiaL The history of the fins and their supports, finally, gives additional evidence as to the modified nature of later Chimasroid development. We may comment, for example, upon the appearance of lobate dorsal fins, the anterior with its spine, at an early period, and the prominence of the paired fins, the pectoral, for example, having at one time a greater proportional siz
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