striped marlin ( Makaira mitgukurii) , while the second group includes the black marlin ( Makaira 

 mazara) and the white marlin ( Makaira marlina ). 



In the family Xiphiidae, that is in the broadbill awordfish ( Xiphias gladius ), the vertebrae 

 differ markedly from those of the istiophorid fishes. Neither the neural nor hemal spines are 

 modified into such flat plates; they present only a somewhat flattened spine shape. Both the 

 neural and hemal processes are remarkably small and only slightly support their respective 

 spines on the next anterior vertebra. The number of vertebrae is also remarkably different, 

 with a total of 26, of which 16 are ventral and 10 caudal, the formula being 16 + 10. 



(c) Jaws 



In the istiophorids the elongated upper jaw is formed of the premaxillary, maxillary, and 

 nasals. The nasals are joined to the frontal, but the union is very weak. The lower jaw is 

 formed of the articular and the dentaries, but the left and right dentary bones are not joined 

 together directly as in other fishes, there being at their anterior ends a triangular bony structure 

 which forms the sharp tip of the lower jaw and into which the dentary bones are articulated. 



The upper jaw is made up in large part of the prema-xillary, the majcillary itself attaining 

 only one-half of the total length. It is narrow and except for the point of articulation with the 

 vomer it is of nearly the same thickness throughout. The nasals make up the dorsal surface of 

 the upper jaw and extend over 3/4 of the total length. They are flat and gradually tapering and 

 are fused to the premaxillary. The upper jaw is not hollow but is almost solid with a fibrous 

 structure like that seen in chips of bamboo. 



Both jaws are covered with tiny cone-shaped bony teeth, but these innumerable teeth do 

 not grow from the jaws, nor are they attached to them. The overall appearance of these teeth 

 is like a rasp, and they are somewhat coarser on the outer edges of both jaws and near the 

 posterior end of the premaxillary. Of course, these teeth are probably of some use when the 

 spearfish seizes its prey, but this objective alone does not suffice as a physiological and mor- 

 phological explanation of these teeth for the reason that the teeth can be seen to exist near the 

 tip of the upper jaw, which is far beyond the tip of the lower jaw. 



There are conspicuous differences anaong the species in the ratio between the lengths of 

 the upper and lower jaws as measured fron-i the posterior end of the msLxillary, this ratio being 

 2, 21 in the black marlin, 2. 19 in the sailfish, 1 . 94 in the white marlin, 1 . 84 in the striped 

 marlin, and 1. 28 in the shortnosed spearfish (see plate 6 and table 3). 



In the broadbill, the upper jaw is made up of the premaxillary, maxillary, and nasals as 

 it is in the istiophorids, but it is markedly different in form. The lower jaw is made up of 

 markedly frailer articular s and dentaries than in the case of the istiophorids. There are no 

 teeth in either of the jaws in adult fish. 



The upper jaw is compressed, its dorsal surface flat and its ventral surface somewhat 

 rounded, the ventral surface being composed of the left and right premaxillaries, which are 

 solidly fused together. The dorsal surface is composed of the maxillary and nasals, all of 

 which reach the whole length of the dorsal surface. All of these bones are solidly fused together 

 so that it is difficult to separate them. ReganL"' in his schematic diagram showing the structure 

 of the upper jaw of the broadbill, has the nasals reaching only half way along the upper jaw, but 

 it is thought that this point requires correction (figure 1), The upper jaw has a box-like hollow 

 center with regular septa forming a ladder-like pattern, presenting the appearance of a longi- 

 tudinally sectioned piece of bamboo. 



— Regan, C. T. , Ann. Mag. Nat. Hist. London, Vol. 3, No. 13, p. 73. 



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