SWORDFISHES. 



117 



the point of llie trabccithr) iiud the ctlniioid lioiic which 

 lies behind and within the rostral portion, wdiile the 

 point and the lateral edges of" the sword are formed 

 by tiie intermaxillary bones. The other differences 

 between the Swordfishes and tlie Sconibi'oids are the 

 round shape of both nostrils and the greater distanee 

 ]3et\vcen the ]iosterioi' nostril and the eye in the former 

 — in whieli respect the Xiphiida; come nearer the 

 Horse-Macl\erels — the smaller size of the subopercu- 

 luni and interopereuhun — the ojjereuhini, liowever, is 

 larger in the Swordfishes — and the smooth, or only 

 slightl\" rugose, anterior edges of tlie l)ranchial arches, 

 where strongly developed gill-rakers appear in the Mac- 

 kerels. The greatest systematic importance of the fa- 

 mily Xipliitd(C consists in the changes due to age which 

 have been given by GOnther" and Lutken' and partly 

 even by Cuviek'', and which we have therefore given 

 in the above diagnosis of the family. First we see the 

 larval stage (fig. 32), with the large eyes; the low, 

 continuous dorsal fin and the similar, but smaller, anal 

 tin; the rounded caudal tin; the broad and short pec- 

 toral fins, wdiich are still set fairh^ high: and the spi- 

 nous equipment of the head, wdiieh reminds us of the 

 Trigloid type or the juvenile forms of the Berycidce''. 

 When the snout and the loAver jaw (the length of which, 

 however, is soon reduced again) begin to grow elong- 

 ated, and the spinous equipment of the head to vanish, 

 there appear other traits of older piscine forms, several 

 scaly formations on the body (fig. 33), rows of spinous 

 plates and scales, one on each side of the bases of the 

 dorsal and anal fins and others, parallel to each other, 

 on the sides, while in the intervals between these rows 

 we find small scales, Avhich also cover the head and 

 snout, also spinous or ciliated. These scaly formations 

 are not imbricate, but juxtaposed. During this period 

 there are also fairly strong jaw^-teeth; the unpaired fins 

 appear as before; the body is long and slender; the 

 caudal fin becomes more and more concave and is also 

 prolonged and pointed like the pectoral fins; and the 

 ventral fins, in those species where they are found, 

 appear in tlie form of small protuberances, which be- 



come elongated and dcNeloj) one or three rays, some- 

 times longer tliaii those of the pectoral fins. We may 

 also see before long, on each side of the tail, the middle 

 carina (in Xipliias) or the two small carinas (in Tetrap- 

 turus and Histiophorus), to which we have above seen 

 corresponding formations in the Scombroids. The sub- 

 se(juent changes are mostly reductions: the disappear- 

 ance of the scaly formations, tlie more or less complete 

 disappearance of the jaw-teeth), the reduction of the 

 middle part of the dorsal and anal fins, the relative 

 diminution of the eves and, lastly, the removal of the 



Fig. 32. Young specimen of a terete-snonteil species of Swordfisli 



{Histiophorus? or Tetrapluriis?) from tlie South Atlantic. 



Magnified 7 diain. After LiJTKEN. 



pectoral fins down towards the ventral edge, "so far,' 

 says Cl'VIER of Xiphias, "that at the first glance one 

 might be tempted to regard them as the ventral fins." 

 In all these changes the Swordfish proper advances 

 furthest: its relations to the other two genera of the 

 family (each containing two or three species) form a 

 distinct chain of development, Hisfiophonis having three 



Fig. 3.3. Young Swordfisli {Xip/iias gladiiis) from the Atlantic. 

 Magnified 2^ „ diam. After LUtken. 



rays in the ventral fins, Tetrapturus two and Xipliias 

 having no ventral fins at all. 



This family, like the greater part of the preceding 

 one, consists of distinctly pelagic fishes and powerful 

 swimmers, which generally keep to the surface — those 

 which retain the high dorsal fin are even said to use 

 it as a sail — but are also able to descend to con- 

 siderable depths. They really belong to the Tropics 

 and the warmer parts of the Temperate Zones, but some- 

 times rove north into our latitudes. 



« Joum. Mus. Godeffr., Heft. 2, p. 170; Heft. 3, p. 265; Introd. Study Fish., pp. 173—175; Handb. Ichth.. pp. 117 and 118. 



* Spol. Atl., 1. c, pp. 441 etc., tab. II, fig. 10 and 11. 



-= Cuv.. Val., Hist. Nat. Poiss., vol. VIII, p. 261, tab. 225 et 226. 



•' According to LOlKEN (1. c, p. 447), however, the long temporal and opercular spines are wanting in the larva? of Xiphias. 



