end is perfectly rounded. In the shortnosed spearfish the upper portion is the shortest among 

 all the species and is somewhat rounded, and the constriction of the central portion is very 

 obscure; the lower end is perfectly rounded. In the broadbill swordfish these bones are com- 

 pletely different in for- and connparison is difficult (plate 7). 



(f) Branchiostegal rays 



Conspicuous differences among the branchiostegal rays of the various species can be 

 seen. The number of these rays in both families of spearfishes is 7. In the white marlin the 

 last ray is remarkably broad, short, and stout, with a roughly triangular form, the other rays 

 being generally long and slender. In the black nnarlin, as has already been stated, the branchio- 

 stegal membrane is short, and consequently the branchiostegal rays are also nnarkedly shorter 

 than in the other species. In the striped marlin all of the branchiostegal rays are rather fila- 

 mentous, they are even slenderer in the sailfish, and in the shortnosed spearfish they are the 

 naost filamentous of all (plate 8). 



In the broadbill the epihyal is strikingly large, and the branchiostegal rays are flat and 

 thin and conspicuously curved. 



(g) Pectoral girdle 



As was stated earlier, in the white marlin the pectoral fins have a special direction of 

 movement and cannot be folded back against the sides of the body. It was thought that the reason 

 for this was probably that the joint between the pectoral fins and the bones which support them 

 was of a peculiar type or that there was some difference in the arrangement of the muscles. 



In the white marlin the articulating surface of the supracoracoid which articulates with 

 the actinotis is almost horizontal, markedly broader than in the other species, and somewhat 

 twisted anterioposteriorly. The anterior margin of the clavicle has a slight concavity on top 

 and only a slight convexity below, being almost straight. In the other istiophorids the articu- 

 lating surface of the supracoracoid with the actinotis is rather oblique, narrow, and is not twisted 

 anterioposteriorly. Except in the striped nnarlin, the anterior edge of the clavicle has a conspi- 

 cuous concavity, but in the striped marlin it is straight and similar in form to that of the white 

 marlin. Rather conspicuous differences between the white marlin and the other species can also 

 be seen in the form of the hypocoracoid, the breadth of the shoulder girdle as a whole is greatest 

 in the white marlin, and the space between the hypocoracoid and the clavicle is greater in this 

 species than in any of the others. As for the form of the hypocoracoid, there is a process which 

 originates at about the middle of its upper edge and which curves back running along the posterior 

 edge. In the white marlin the origin of the process is conspicuously large, but the process as 

 a whole is blunt and quickly becomes obscure. A roughly triangular projection on the upper rear 

 edge of the hypocoracoid is turned noticeably upward in the white marlin and shortnosed spearfish. 



In the other species of the family Istiophoridae the pectoral girdle is in general narrow and 

 the space between it and the clavicle is small; the process discussed above is sharp andjconspi- 

 cuous and extends all along the edge of the bone. The upper rear edge of the coracoid /evidently 

 hypocoracoid is meant/ is almost horizontal (plate 9). 



(h) Pelvic girdle Jind ventral fins 



The pelvic girdle and ventral fins are lacking in the broadbill. In the Istiophoridae the 

 pelvic girdle is well developed and is rather palmate in shape. Its structure falls into two types, 

 of which one appears in the white marlin and the other in the rest of the species. As is shown in 

 plate 9, in the former the right and left sides of the pelvic girdle are fused together and are 

 difficult to separate, while in the latter typie there is a broad space between the two sides and 

 they cam easily be separated. 



Hitherto it has been considered that the number of rays in the ventral fins was 1 to 3 in the 

 Istiophoridae with 1 in all species of the genus Tetrapturus and 3 only in the genus Istiophorus , 



19 



