116 



SCANDINAVIAN FISHES. 



fisherman chooses a different deptli of ^vater according 

 to the season: as the season advances, the Mackerel 

 gradually' goes into deeper water, a fairly sure sign 

 that it is on its way back to the deep sea. 



On the west coast of Norway, according to H. 

 Baars {Die Fischereiindustrie Norwegens, Bergen 1873, 



p. 58), about 2,500 boats are engaged in this fishery, 

 and the annual catch is from 30 to 35 million Macke- 

 rel. The Mackerel-fishery is carried on on a still larger 

 scale oft" the east coast of North Atnerica (see note a, 

 p. 114), \vhere the tackle employed consists chiefly of 

 purse-seines". (Ekstkom, Smitt.) 



fam xiphiidj:. 



B()(hi fusiform and elongated. Eyes middle-sized. Both, the preopercuJiim and the supraorbital margins dentated 

 during gouth'', smooth (like the other bones of the head) in full-grown specimens. The scales vanish during growth, 

 in young specimens they are ciliated and some of them platelike and spinous. During youth one continuous fin 

 on the back and in the anal region, hut in full-grown specimens a greater or less part of the middle of these fins 

 disappears, and thus two dorsal and two anal fins are formed, the anterior being, in both cases, larger than the 

 posterior. No free spinous ray in front of the anal fin. Simple, pointed conical teeth in both jaws during youth; 

 but they finally disappear in quite fuU-grown specimens'. During youth both jaivs are more or less elongated in 

 a forward direction, the upper more than the lower, but in full-grown specimens the lower jaw is still more con- 

 siderably shorter than the upper, which is prolonged into a "sword," formed by the maxillary and intermaxillary 

 bones, the vomer {rostral part) and the ethmoid bone. The superior longitudinal ridges on the .skull are only 

 slightly or not at all developed. In the species where there are ventral fins, they are thoracic, and the number of 

 raifs is less than usual, in other cases they are wanting. Gill-openings large., but the branchiostegal membranes 

 partly united. Branchiostegal rays 7. Branched rays in the caudal fin at least 15. Vertebrce at least 24, more 



than 10 of them abdominal. 



Agassiz'' separated this family from the Cuvierian 

 Scombroids "in order more clearly to fix the characters 

 of the latter;" Ijut it is not Avithout reason that botli 

 LuTKEN*" and Lii-ljeborg' liave suggested the reunion 

 of these two families. It is not only that at least one 

 genus of the Scombroids (Acanthocybium) has the same 

 retiform branchial lamelhe as the Swordfishes (see above), 

 nor that in the latter this coalescent formation of the 

 branchial lamellte does not apj)ear during youth'', but 

 also that the osteological characters, to which Agassiz 

 gave the first ])lace in his diagnosis of the Swordfishes, 

 to a great extent correspond to those of the Mackerels. 

 The remarkable structure in the Swordfishes of the 

 ha'uiapophyses of the caudal vertebra?, which consist of 

 broad processes beneath the lateral holes of the haemal 

 canal and the consequent articulation between the haemal 



arches of the successive vertebras, apparently corresponds 

 to the structure of the caudal vertebra' ^vhich we have 

 remarked above in Euthynnus. The strong connecting- 

 links in the Swordfishes between the interspinal bones 

 and also between the interha?mal, which are formed 

 Ijy the sagittal extensions of these bones, and side 

 by side with which the neural and the luismal spines 

 are also extraordinarily broad (extended in the same 

 direction, the longitudinal direction of the body), are 

 indeed wanting in tiie Mackerels; but still they are 

 caused only by a stronger ossification of the membrane 

 between these bones, which even in the Mackerels is 

 sometimes fairly hard. The family character of the 

 Swordfishes is thus the ensiform (sometimes cuneiform 

 and terete) elongation of the snout, the chief part of 

 which is composed of the rostral portion (original]}^ 



" See also Materials for a IJigtorij of the Mackerel Fishery by G. Bkown-Goode, J. W. Collins, R. E. Earll, and A H. Clark, Rep. 

 Cumiii. Fish. a. Fisher. 1881 (Washington 1884) pp. 91 — 631. 



'' In some species the corners of tlie temples (according to GUntiier, the parietal bones) and of the preopereiiluni are prolonged into 

 strong spines, which call to mind the Trigloid type. 



"■ In a Swordfish which has attained a length of 8 feet we find small, but numerous, teeth on the hind part of the intermaxillary bones. 



'' Rech. Poiss. FoKS., tome V, jiart. 1, jip. 1, 7 and 89. 



^ LOtken, ^pol. Atl., Vid. S.dsk. Skr., Kbhvn., 6:te Rad<ke, Naturv. Math. Afd., vol. XII, p. 447. 



'' jSv. Norg. Fiskar, vol. I, p. 379, not. 1. 



'J Ll'tkkn, 1. e., p. 44G. 



