A history of the fishes of Madeira / by Richard Thomas Lowe ... With original figures from nature of all the species, by the Hon. C.E.C. Norton and M. Young.

  • Richard Thomas Lowe
Date:
1843-1860
Catalogue details

Licence: Public Domain Mark

Credit: A history of the fishes of Madeira / by Richard Thomas Lowe ... With original figures from nature of all the species, by the Hon. C.E.C. Norton and M. Young. Source: Wellcome Collection.

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    thyologists. The close alliance naturally of Telragonurus with the Scombridal genera Thyrsites, or Aplurus (Escolar), may be inferred both from its being called vernacularly Escolar de natura, and from the true Scombridal Escolar having, though erroneously, been supposed to belong to the same genus. Indeed there seems little either of external character or inward struc- ture to warrant the arrangement of this fish amongst the Mugilidae. These have few caeca, Tetragonurus having many: in the true Grey Mullets the ascending branch of the stomach dilates into a sort of giz- zard; in Tetragonurus it is simple: they have few vertebrae; Tetra- gonurus has many: they have minute and feeble or setaceous teeth; it has them distinct and bony: they have the palatines and vomer normally unarmed; it has them armed: they have smooth and apparently entire scales * * * § ; it has them rough and pectinato-ciliate. In Tetragonurus the form of the fins, especially of the two dorsal fins, and the nature of their rays differ remarkably from the usual character of these parts in the Mu- gilidee; and the anatomical structure of the pharynx, mouth, and teeth, has nothing whatever of the peculiar organization which characterizes so singularly the Grey Mullets. The pseudo-abdominal or backward posi- tion of the ventral a little behind the root of the pectoral fins, is a very trifling, fallacious character when resting as here, and in many other Acanthopterygious fishes,]; on mere external appearances : and if insuf- ficient for a ground of association with the Grey Mullets, it is absolutely of no value whatever as a mark to separate Tetragonurus from the Scom- bridae. Guv.; for the ventral fins, or their rudiments, in a crowd of these, § are equally behind the pectoral, and are vastly more so in Nota- * A high power of the microscope shows, indeed, that the edges of their laminae in Mugil are finely crenulate : in which, if not sui generis, they may he perhaps considered to approach rather to the ctenoidal, than to be of the true cycloidal structure. But if this serve not for a caution against employing too absolutely the intimate formation of the scales in founding or defining the main ich- thine divisions, it shows at least the liability to practical uncertainty attendant on these characters. In the ScomhridcB, normally the scales are truly cycloidal: in the Mugilidce, they are only so ap- parently, or ambiguously : in Tetragonurus, otherwise Scombridal, they are eminently and distinctly ctenoid. Thus the character in which Tetragonurus approaches, according to this theory, nearest to the Mugilidce, is the very point in which it most appears, except on microscopical investigation, to differ from them. And even after appeal to the microscope, it might truly be affirmed that there is no stronger discrepancy between the scale of a true Scombridal fish and of a Mugil, than between one of the latter and of a Tetragonurus. This genus may, however, be considered as in several re- spects connecting Alugilidce with ScomhridcB. + See Cuv. and Val. Hist. iii. 67 ; ih. xi. 195.—The ventral fins in Tetragonurus are not truly abdominal or unconnected with the bones of the shoulder, as in the Abdominal Malacopterygians, or the Acanthopterygian Sphyrcenidm. + The ventral fins are quite as abdominal, apparently, in the typically thoracic genus Perea, as in Tetragonurus and the Grey Midlets. § E. g. Lampris, Scomber, Thyrsites, Gcmpylus proper, Lcpidop)us, Aplurus, some species of Lichia, Caraax, &c.