FOOTNOTES:
[1] From ιχθυς, fish, and λογος, doctrine or treatise.
[2] Down to this period the history of Ichthyology is fully treated in the first volume of Cuvier and Valenciennes “Hist. nat. d. Poiss.”
[3] Description of Ceratodus. “Phil. Trans.,” 1871, ii.
[4] In the formula generally preceding the description of a fish, “L. lat. 40,” would express that the scales between the head and caudal fin are arranged in 40 transverse series; and probably, that the lateral line is composed of the same number of scales. “L. transv. 8/5” would express that there are eight longitudinal series of scales between the median line of the back and the lateral line, and five between the lateral line and the middle of the abdomen.
[5] Pterotic of Parker.
[6] C. Hasse has studied the modifications of the texture of the vertebræ and the structure of the Chondropterygian skeleton generally, and shown that they correspond in the main to the natural groups of the system, and, consequently, that they offer a valuable guide in the determination of fossil remains.
[7] The Ganoids formed at former epochs the largest and most important order of fishes, many of the fossil forms being known from very imperfect remains only. It is quite possible that not a few of the latter, in which nothing whatever of the (probably very soft) endoskeleton has been preserved, should have to be assigned to some other order lower in the scale of organisation than the Ganoids (for instance, the Cephalaspidæ).
[8] As first proposed by Huxley.
[9] Stannius (pp. 60, 65) doubts the pure origin of these two bones from membranous tissue, and is inclined to consider them as “the extreme end of the abortive axial system.”
[10] Parker’s nomenclature is adopted here.
[11] According to Langerhans “Untersuchungen über Petromyzon planeri” (Freiburg, 1873) an optic chiasma exists in that species.
[12] This nerve is not shown in the figure of the brain of the Perch (Fig. 41), as reproduced above from Cuvier.
[13] Müller considers a nerve rising jointly with the Vagus in Petromyzon to be this nerve (Fig. 45, hy).
[14] On the development and structure of the dentition of Scarina, see Boas, “Die Zähne der Scaroiden,” in Zeitschr. f. Wiss. Zoolog. xxxii. (1878).
[15] This applies to individuals only growing up under normal conditions. Dr. H. A. Meyer has made observations on young Herrings. Individuals living in the sea had attained at the end of the third month a length of 45 to 50 millimetres, whilst those reared from artificially-impregnated ova were only from 30 to 35 millimetres long. When the latter had been supplied with more abundant food, they grew proportionally more rapidly in the following months, so that at the end of the fifth month they had reached the same length as their brethren in the sea, viz. a length of 65 to 70 millimetres.
[16] Ray Lankester considers it to be a portion of the long denticulated cornua of a genus Eukeraspis allied to Cephalaspis.
[17] Ekström, Fische in den Scheeren von Mörkö.
[18] Will probably be found.
[19] We distinguish these sub-regions, because their distinction is justified by other classes of animals; as regards freshwater fishes their distinctness is even less than that between Europe and Northern Asia.
[20] Martens (Preuss. Exped. Ostas. Zool. i. p. 356), has already drawn attention that a Barbel, said to have been obtained by Ida Pfeiffer in Amboyna (Günth. Fish. vii. p. 123), cannot have come from that locality.
[21] In the following and succeeding lists, those forms which are peculiar to and exclusively characteristic of, the region, are printed in italics; the other regions, in which the non-peculiar forms occur, are mentioned within brackets [].
[22] Lates calcarifer in India as well as Australia.
[23] One species (Arius thalassinus) found in Indian and African rivers.
[24] This species extends from India into East Africa.
[25] We have left out from these considerations the Ariina and Cyprinodonts, which can pass with impunity through salt water, and are spread over much larger areas.
[26] Cope has discovered in a tertiary freshwater-deposit at Idaho an extinct genus of this group, Diastichus. He considers this interesting fact to be strongly suggestive of continuity of territory of Asia and North America.—“Proc. Am. Phil. Soc. 1873,” p. 55.
[27] Leidy describes a Siluroid (Pimelodus) from tertiary deposits of Wyoming Territory. “Contrib. to the Extinct Vert. Fauna of the Western Territ. 1873,” p. 193.
[28] The genera peculiar to the Equatorial zone are printed in italics.
[29] Number of species uncertain.
[30] See p. 151, Fig. 67.
[31] See p. 128, Fig. 55.
[32] See p. 104.
[33] See p. 167, Figs. 79, 81.
[34] See p. 136, Fig. 58.
[35] See p. 167, Fig. 78.
[36] The cartilaginous jaws of Sharks shrink at least a third in drying, and, therefore, cannot be kept at full stretch without tearing.
[37] This exception is a Ray obtained during the “Challenger” expedition, and said to have been dredged in 565 fathoms.
[38] See pp. 73 and 74, Figs. 35 and 36.
[39] For other illustrations see p. 73, Fig. 35 (palatal view of head); p. 74, Fig. 36 (pectoral skeleton); p. 141, Fig. 60 (gills); p. 148, Fig. 65 (lung); p. 151, Fig. 67 (heart); p. 134, Fig. 57 (intestine); p. 165, Fig. 77 (ovary).
[40] See p. 97, Fig. 41; and p. 152, Fig. 68.
[41] The Acanthopterygians do not form a perfectly natural group, some heterogeneous elements being mixed up with it. Neither are the characters, by which it is circumscribed, absolutely distinctive. In some forms (certain Blennioids) the structure of the fins is almost the same as in Anacanths; there are some Acanthopterygians, as Gerres, Pogonias, which possess coalesced pharyngeals; and, finally, the presence or absence of a pneumatic duct loses much of its value as a taxonomic character when we consider that probably in all fishes a communication between pharynx and air-bladder exists at an early stage of development.
[42] In this instance, one may entertain reasonable doubts as to the usefulness of the Pilot to the Shark.
[43] Mackerel, like other marine fishes, birds, and mammals of prey, follow the shoals of young and adult Clupeoids in their periodical migrations; on the British coasts it is principally the fry of the Pilchard and Sprat which wanders from the open sea towards the coast, and guides the movements of the Mackerel.
[44] The systematic affinities of these extinct genera are very obscure. Cope places them, with others (for instance Protosphyræna, which has a sword-like prolongation of the ethmoid), in a distinct family, Saurodontidæ: see “Vertebrata of the Cretaceous Formations of the West,” 1875.
[45] For specific characters and detailed descriptions we refer to Günther, “Catal. of Fishes,” vol. vi.
[46] The names “Bull-trout” and “Peal” are not attributable to definite species. We have examined specimens of S. salar, S. trutta, and S. cambricus and S. fario, to which the name “Bull-trout” had been given; and that of “Peal” is given indiscriminately to Salmon-grilse and to S. cambricus.
[47] Fig. 317 is taken from a specimen in which the horny covers of the dentition were lost, hence it does not represent accurately the shape of the teeth.
[48] This name is two years older than Amphioxus.
Transcriber’s Notes:
1. Obvious printers’, punctuation and spelling errors have been corrected silently.
2. Where hyphenation is in doubt, it has been retained as in the original.
3. Some hyphenated and non-hyphenated versions of the same words have been retained as in the original.